Fix the documentation for the return type of model export functions.

PiperOrigin-RevId: 296307536

tensorflow_estimator/python/estimator/estimator.py

@@ -706,7 +706,7 @@ def export_saved_model(self,
         be exported. Note that this feature is experimental.
 
     Returns:
-      The string path to the exported directory.
+      The path to the exported directory as a bytes object.
 
     Raises:
       ValueError: if no `serving_input_receiver_fn` is provided, no
@@ -790,7 +790,7 @@ def experimental_export_all_saved_models(self,
         the most recent checkpoint found within the model directory is chosen.
 
     Returns:
-      The string path to the exported directory.
+      The path to the exported directory as a bytes object.
 
     Raises:
       ValueError: if any `input_receiver_fn` is `None`, no `export_outputs`
@@ -1724,7 +1724,7 @@ def export_savedmodel(self,
         https://github.com/tensorflow/tensorflow/blob/master/tensorflow/python/saved_model/README.md#stripping-default-valued-attributes).
 
     Returns:
-      The string path to the exported directory.
+      The path to the exported directory as a bytes object.
 
     Raises:
       ValueError: if no `serving_input_receiver_fn` is provided, no