code: def childIds(self):
          
          if self.depth >= len(self.citation.root):
              return []
          elif self._children is not None:
              return self._children
          else:
              self._children = self.getReffs()
              return self._children
docs: Children of the passage
  
          :rtype: None, CtsReference
          :returns: Dictionary of chidren, where key are subreferences