code: def get_node_mapping(H):
      
      node_set = H.get_node_set()
      nodes_to_indices, indices_to_nodes = {}, {}
  
      node_index = 0
      for node in node_set:
          nodes_to_indices.update({node: node_index})
          indices_to_nodes.update({node_index: node})
          node_index += 1
  
      return indices_to_nodes, nodes_to_indices
docs: Generates mappings between the set of nodes and integer indices (where
      every node corresponds to exactly 1 integer index).
  
      :param H: the hypergraph to find the node mapping on.
      :returns: dict -- for each integer index, maps the index to the node.
                dict -- for each node, maps the node to the integer index.