Make submodules the preferred names, except for modules, they should prefer the root.

Prefer `tf.submodule.Symbol` to `tf.Symbol`.
When the object is a module, then prefer
`tf.submodule` over `tf.package.submodule` so that `tf.submodule.Symbol` finds `tf.submodule`.

PiperOrigin-RevId: 235278774

tensorflow/tools/docs/doc_generator_visitor.py

@@ -194,10 +194,11 @@ class DocGeneratorVisitor(object):
       contrib_score = 1
 
     while parts:
-      parts.pop()
       container = self._index['.'.join(parts)]
       if tf_inspect.ismodule(container):
         break
+      parts.pop()
+
     module_length = len(parts)
     if len(parts) == 2:
       # `tf.submodule.thing` is better than `tf.thing`