docs: def add_parent(self,node):
      """
      Add a parent to this node. This node will not be executed until the
      parent node has run sucessfully.
      @param node: CondorDAGNode to add as a parent.
      """
      if not isinstance(node, (CondorDAGNode,CondorDAGManNode) ):
        raise CondorDAGNodeError, "Parent must be a CondorDAGNode or a CondorDAGManNode"
      self.__parents.append( node )