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 )
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.