code: def document(self, *document_path):
          
          if len(document_path) == 1:
              path = document_path[0].split(_helpers.DOCUMENT_PATH_DELIMITER)
          else:
              path = document_path
  
          return DocumentReference(*path, client=self)
docs: Get a reference to a document in a collection.
  
          For a top-level document:
  
          .. code-block:: python
  
              >>> client.document('collek/shun')
              >>> # is the same as
              >>> client.document('collek', 'shun')
  
          For a document in a sub-collection:
  
          .. code-block:: python
  
              >>> client.document('mydocs/doc/subcol/child')
              >>> # is the same as
              >>> client.document('mydocs', 'doc', 'subcol', 'child')
  
          Documents in sub-collections can be nested deeper in a similar fashion.
  
          Args:
              document_path (Tuple[str, ...]): Can either be
  
                  * A single ``/``-delimited path to a document
                  * A tuple of document path segments
  
          Returns:
              ~.firestore_v1beta1.document.DocumentReference: A reference
              to a document in a collection.