Update docstrings for st.form, st.toast, st.date_input
diff --git a/lib/streamlit/elements/form.py b/lib/streamlit/elements/form.py
index 00de2795eeca..80e8ebc22507 100644
--- a/lib/streamlit/elements/form.py
+++ b/lib/streamlit/elements/form.py
@@ -134,9 +134,8 @@ def form(self, key: str, clear_on_submit: bool = False) -> DeltaGenerator:
         * ``st.button`` and ``st.download_button`` cannot be added to a form.
         * Forms can appear anywhere in your app (sidebar, columns, etc),
           but they cannot be embedded inside other forms.
-
-        For more information about forms, check out our
-        `blog post <https://blog.streamlit.io/introducing-submit-button-and-forms/>`_.
+        * Within a form, the only widget that can have a callback function is
+          ``st.form_submit_button``.
 
         Parameters
         ----------
@@ -167,6 +166,10 @@ def form(self, key: str, clear_on_submit: bool = False) -> DeltaGenerator:
         ...
         >>> st.write("Outside the form")
 
+        .. output::
+           https://doc-form1.streamlit.app/
+           height: 425px
+
         Inserting elements out of order:
 
         >>> import streamlit as st
@@ -178,6 +181,10 @@ def form(self, key: str, clear_on_submit: bool = False) -> DeltaGenerator:
         >>> # Now add a submit button to the form:
         >>> form.form_submit_button("Submit")
 
+        .. output::
+           https://doc-form2.streamlit.app/
+           height: 375px
+
         """
         # Import this here to avoid circular imports.
         from streamlit.elements.utils import check_session_state_rules
diff --git a/lib/streamlit/elements/time_widgets.py b/lib/streamlit/elements/time_widgets.py
index 6a14e845a1ce..75fe0f962ac1 100644
--- a/lib/streamlit/elements/time_widgets.py
+++ b/lib/streamlit/elements/time_widgets.py
@@ -488,19 +488,38 @@ def date_input(
         datetime.date or a tuple with 0-2 dates
             The current value of the date input widget.
 
-        Example
-        -------
+        Examples
+        --------
         >>> import datetime
         >>> import streamlit as st
         >>>
-        >>> d = st.date_input(
-        ...     "When\'s your birthday",
-        ...     datetime.date(2019, 7, 6))
+        >>> d = st.date_input("When's your birthday", datetime.date(2019, 7, 6))
         >>> st.write('Your birthday is:', d)
 
         .. output::
            https://doc-date-input.streamlit.app/
-           height: 260px
+           height: 380px
+
+        >>> import datetime
+        >>> import streamlit as st
+        >>>
+        >>> today = datetime.datetime.now()
+        >>> next_year = today.year + 1
+        >>> jan_1 = datetime.date(next_year, 1, 1)
+        >>> dec_31 = datetime.date(next_year, 12, 31)
+        >>>
+        >>> d = st.date_input(
+        ...     "Select your vacation for next year",
+        ...     (jan_1, datetime.date(next_year, 1, 7)),
+        ...     jan_1,
+        ...     dec_31,
+        ...     format="MM.DD.YYYY",
+        ... )
+        >>> d
+
+        .. output::
+           https://doc-date-input1.streamlit.app/
+           height: 380px
 
         """
         ctx = get_script_run_ctx()
diff --git a/lib/streamlit/elements/toast.py b/lib/streamlit/elements/toast.py
index e7aeb65d93f4..0582a47807e2 100644
--- a/lib/streamlit/elements/toast.py
+++ b/lib/streamlit/elements/toast.py
@@ -44,6 +44,11 @@ def toast(
         """Display a short message, known as a notification "toast".
         The toast appears in the app's bottom-right corner and disappears after four seconds.
 
+        .. warning::
+            ``st.toast`` is not compatible with Streamlit's `caching \
+            <https://docs.streamlit.io/library/advanced-features/caching>`_ and
+            cannot be called within a cached function.
+
         Parameters
         ----------
         body : str

Update st.form docstring to include embedded apps and link to new forms guide. Update st.toast docstring to warn against use within cached functions. Update st.date_input docstring to add example and embedded app showing date format.

## Describe your changes
Docsting-only edit to st.form, st.toast, st.date_input

## Testing Plan
None. Documentation only.

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