make update to docs about typing model ivars (Azure#28217)

* make update about typing model ivars

* add that ivar docstrings and redundant, not that they aren't needed

* offline feedback

* missing param docstring for kind

Author: kristapratico

doc/dev/static_type_checking_cheat_sheet.md

@@ -50,14 +50,30 @@ class KeyCredential:
         ...
 ```
 
-- Do provide type annotations for all instance variables on a model. You can do this by typing the parameters in the 
-  `__init__` or by adding type hints directly to the instance variables.
+- Do provide type annotations for all public instance variables on a model. Do this by adding class-level type hints
+per [PEP526](https://peps.python.org/pep-0526/).
 
 ```python
 class Tree:
-
-    def __init__(self, *, location: str, num_branches: int) -> None:
-        self.kind: typing.Literal["oak"] = "oak"
+    """Represents a tree.
+
+    :param str location: The location for the tree.
+    :param int num_branches: The number of branches on the tree
+    :param str kind: The kind of tree.
+    
+    Note: :ivar: docstrings are redundant since these vars/types are captured below
+    """
+
+    location: str
+    """A description of the location of the tree."""
+    num_branches: int
+    """Number of branches on tree."""
+    kind: str = "oak"
+    """The kind of tree."""
+
+    def __init__(self, *, location: str, num_branches: int, kind: Optional[str] = None) -> None:
+        if kind: 
+            self.kind = kind
         self.location = location
         self.num_branches = num_branches
 ```