code: def _is_child(self, parent, child):  # type: (str, str) -> bool
          
          parent_parts = tuple(self._split_table_name(parent))
          child_parts = tuple(self._split_table_name(child))
  
          if parent_parts == child_parts:
              return False
  
          return parent_parts == child_parts[: len(parent_parts)]
docs: Returns whether a key is strictly a child of another key.
          AoT siblings are not considered children of one another.