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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def add_node(self,node):
 """ Add a CondorDAGNode to this DAG. The CondorJob that the node uses is also added to the list of Condor jobs in the DAG so that a list of the submit files needed by the DAG can be maintained. Each unique CondorJob will be added once to prevent duplicate submit files being written. @param node: CondorDAGNode to add to the CondorDAG. """

    if not isinstance(node, CondorDAGNode):
      raise CondorDAGError, "Nodes must be class CondorDAGNode or subclass"
    if not isinstance(node.job(), CondorDAGManJob):
      node.set_log_file(self.__log_file_path)
    self.__nodes.append(node)
    if self.__integer_node_names:
      node.set_name(str(self.__node_count))
    self.__node_count += 1
    if node.job() not in self.__jobs:
      self.__jobs.append(node.job())