'Merge two given states, and return a new one.
:param old_state:
:param new_state:
:returns: The merged state, and whether a merging has occurred'

def _merge_states(self, old_state, new_state):

    (merged_state, _, merging_occurred) = old_state.merge(new_state, plugin_whitelist=self._mergeable_plugins)
    return (merged_state, merging_occurred)
