[keras/layers/pooling] Standardise docstring usage of "Default to"
diff --git a/keras/layers/pooling/average_pooling2d.py b/keras/layers/pooling/average_pooling2d.py
index b818ed7e3a8..662ec99016e 100644
--- a/keras/layers/pooling/average_pooling2d.py
+++ b/keras/layers/pooling/average_pooling2d.py
@@ -108,9 +108,10 @@ class AveragePooling2D(Pooling2D):
         `(batch, height, width, channels)` while `channels_first`
         corresponds to inputs with shape
         `(batch, channels, height, width)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
 
     Input shape:
       - If `data_format='channels_last'`:
diff --git a/keras/layers/pooling/average_pooling3d.py b/keras/layers/pooling/average_pooling3d.py
index 41faa234aeb..9d1177e6c68 100644
--- a/keras/layers/pooling/average_pooling3d.py
+++ b/keras/layers/pooling/average_pooling3d.py
@@ -48,9 +48,10 @@ class AveragePooling3D(Pooling3D):
         `(batch, spatial_dim1, spatial_dim2, spatial_dim3, channels)`
         while `channels_first` corresponds to inputs with shape
         `(batch, channels, spatial_dim1, spatial_dim2, spatial_dim3)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
 
     Input shape:
       - If `data_format='channels_last'`:
diff --git a/keras/layers/pooling/global_average_pooling2d.py b/keras/layers/pooling/global_average_pooling2d.py
index beb7038122c..e219e241408 100644
--- a/keras/layers/pooling/global_average_pooling2d.py
+++ b/keras/layers/pooling/global_average_pooling2d.py
@@ -44,9 +44,9 @@ class GlobalAveragePooling2D(GlobalPooling2D):
           `(batch, height, width, channels)` while `channels_first`
           corresponds to inputs with shape
           `(batch, channels, height, width)`.
-          It defaults to the `image_data_format` value found in your
-          Keras config file at `~/.keras/keras.json`.
-          If you never set it, then it will be "channels_last".
+          When unspecified, uses `image_data_format` value found
+          in your Keras config file at `~/.keras/keras.json`
+          (if exists) else 'channels_last'. Defaults to 'channels_last'.
         keepdims: A boolean, whether to keep the spatial dimensions or not.
           If `keepdims` is `False` (default), the rank of the tensor is reduced
           for spatial dimensions.
diff --git a/keras/layers/pooling/global_average_pooling3d.py b/keras/layers/pooling/global_average_pooling3d.py
index b2819c55164..04b95667ed8 100644
--- a/keras/layers/pooling/global_average_pooling3d.py
+++ b/keras/layers/pooling/global_average_pooling3d.py
@@ -36,9 +36,10 @@ class GlobalAveragePooling3D(GlobalPooling3D):
         `(batch, spatial_dim1, spatial_dim2, spatial_dim3, channels)`
         while `channels_first` corresponds to inputs with shape
         `(batch, channels, spatial_dim1, spatial_dim2, spatial_dim3)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
       keepdims: A boolean, whether to keep the spatial dimensions or not.
         If `keepdims` is `False` (default), the rank of the tensor is reduced
         for spatial dimensions.
diff --git a/keras/layers/pooling/global_max_pooling2d.py b/keras/layers/pooling/global_max_pooling2d.py
index 3ef2ee74a54..77ef11b3abd 100644
--- a/keras/layers/pooling/global_max_pooling2d.py
+++ b/keras/layers/pooling/global_max_pooling2d.py
@@ -42,9 +42,10 @@ class GlobalMaxPooling2D(GlobalPooling2D):
         `(batch, height, width, channels)` while `channels_first`
         corresponds to inputs with shape
         `(batch, channels, height, width)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
       keepdims: A boolean, whether to keep the spatial dimensions or not.
         If `keepdims` is `False` (default), the rank of the tensor is reduced
         for spatial dimensions.
diff --git a/keras/layers/pooling/global_max_pooling3d.py b/keras/layers/pooling/global_max_pooling3d.py
index ee153d9c3cd..f5385fc9b41 100644
--- a/keras/layers/pooling/global_max_pooling3d.py
+++ b/keras/layers/pooling/global_max_pooling3d.py
@@ -34,9 +34,10 @@ class GlobalMaxPooling3D(GlobalPooling3D):
         `(batch, spatial_dim1, spatial_dim2, spatial_dim3, channels)`
         while `channels_first` corresponds to inputs with shape
         `(batch, channels, spatial_dim1, spatial_dim2, spatial_dim3)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
       keepdims: A boolean, whether to keep the spatial dimensions or not.
         If `keepdims` is `False` (default), the rank of the tensor is reduced
         for spatial dimensions.
diff --git a/keras/layers/pooling/max_pooling2d.py b/keras/layers/pooling/max_pooling2d.py
index 7378d3d91a9..f21ab07f214 100644
--- a/keras/layers/pooling/max_pooling2d.py
+++ b/keras/layers/pooling/max_pooling2d.py
@@ -127,9 +127,10 @@ class MaxPooling2D(Pooling2D):
         `(batch, height, width, channels)` while `channels_first`
         corresponds to inputs with shape
         `(batch, channels, height, width)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
 
     Input shape:
       - If `data_format='channels_last'`:
diff --git a/keras/layers/pooling/max_pooling3d.py b/keras/layers/pooling/max_pooling3d.py
index b0455dbf4d4..64b2575732e 100644
--- a/keras/layers/pooling/max_pooling3d.py
+++ b/keras/layers/pooling/max_pooling3d.py
@@ -48,9 +48,10 @@ class MaxPooling3D(Pooling3D):
         `(batch, spatial_dim1, spatial_dim2, spatial_dim3, channels)`
         while `channels_first` corresponds to inputs with shape
         `(batch, channels, spatial_dim1, spatial_dim2, spatial_dim3)`.
-        It defaults to the `image_data_format` value found in your
-        Keras config file at `~/.keras/keras.json`.
-        If you never set it, then it will be "channels_last".
+        When unspecified, uses
+        `image_data_format` value found in your Keras config file at
+         `~/.keras/keras.json` (if exists) else 'channels_last'.
+        Defaults to 'channels_last'.
 
     Input shape:
       - If `data_format='channels_last'`:

This is one of many PRs. Discussion + request to split into multiple PRs @ #17748