code: def get_all_children(self):
          
          children = self._children[:]
          oldlen = 0
          newlen = len(children)
          while oldlen != newlen:
              start = oldlen
              oldlen = len(children)
              for i in range(start, len(children)):
                  children.extend(children[i]._children)
              newlen = len(children)
          return children
docs: Get all children including children of children
  
          :returns: all children including children of children
          :rtype: list of :class:`Reftrack`
          :raises: None