docs: def library_hierarchy_depth(self):
          """ Calculates the library hierarchy depth
  
          Counting starts at the current library state. So if the there is no upper library state the depth is one.
          
          :return: library hierarchy depth
          :rtype: int
          """
          current_library_hierarchy_depth = 1
          library_root_state = self.get_next_upper_library_root_state()
          while library_root_state is not None:
              current_library_hierarchy_depth += 1
              library_root_state = library_root_state.parent.get_next_upper_library_root_state()
          return current_library_hierarchy_depth