Flesh out the documentation a bit

Author: tmke8

docs/source/command_line.rst

@@ -503,8 +503,21 @@ potentially problematic or redundant in some way.
     being instantiated which has attributes that were declared but never
     initialized.
 
-    (TODO: give examples)
+    For example, in the following code, mypy will warn that ``value`` was not
+    initialized.
+
+    .. code-block:: python
+
+        class Foo:
+            value: int
+            def __init__(self) -> None:
+                self.vaelu = 3  # typo in variable name
+        foo = Foo()  # Error: 'value' is uninitialized
+
+    .. note::
 
+        Mypy cannot properly detect initialization in very dynamic code like
+        classes with a custom ``__new__`` method.
 
 .. _miscellaneous-strictness-flags: