[NFC] polish colossalai/builder/builder.py code style
diff --git a/colossalai/builder/builder.py b/colossalai/builder/builder.py
index f4ccebfc7a2f..812ab78d7ab6 100644
--- a/colossalai/builder/builder.py
+++ b/colossalai/builder/builder.py
@@ -7,6 +7,7 @@
 from colossalai.registry import *
 
 
+
 def build_from_config(module, config: dict):
     """Returns an object of :class:`module` constructed from `config`.
 
@@ -64,6 +65,7 @@ def build_from_registry(config, registry: Registry):
     return obj
 
 
+
 def build_layer(config):
     """Returns a layer object of :class:`nn.Module` constructed from `config`.
 
@@ -243,7 +245,6 @@ def build_lr_scheduler(config, optimizer):
     config_['optimizer'] = optimizer
     return build_from_registry(config_, LR_SCHEDULERS)
 
-
 def build_schedule(config):
     """Returns a schedule of :class:`colossalai.engine.schedule.BaseSchedule`.
 
