code: def remove_umis(adj_list, cluster, nodes):
      '''removes the specified nodes from the cluster and returns
      the remaining nodes '''
  
      # list incomprehension: for x in nodes: for node in adj_list[x]: yield node
      nodes_to_remove = set([node
                             for x in nodes
                             for node in adj_list[x]] + nodes)
  
      return cluster - nodes_to_removf remove_umis(adj_list, cluster, nodes):
      '''removes the specified nodes from the cluster and returns
      the remaining nodes '''
  
      # list incomprehension: for x in nodes: for node in adj_list[x]: yield node
      nodes_to_remove = set([node
                             for x in nodes
                             for node in adj_list[x]] + nodes)
  
      return cluster - nodes_to_remove
docs: removes the specified nodes from the cluster and returns
      the remaining nodes