Update contents.rst

docs/source/extending/contents.rst

@@ -100,9 +100,10 @@ model. There are three model types: **notebook**, **file**, and **directory**.
    .. _contentfree:
 
    In certain circumstances, we don't need the full content of an entity to
-   complete a Contents API request.  In such cases, we omit the ``content``, and
-   ``format`` keys from the model, and the default values for the ``mimetype``
-   field (see above). This most commonly occurs when listing a directory, in
+   complete a Contents API request. In such cases, we omit the ``content``, and
+   ``format`` keys from the model. The default values for the ``mimetype``
+   field will might also not be evaluated, in which case it will be set as `None`.
+   This reduced reply most commonly occurs when listing a directory, in
    which circumstance we represent files within the directory as content-less
    models to avoid having to recursively traverse and serialize the entire
    filesystem.