code: def _save(self, filename):
      with open(filename, "w") as file:
          file.write(
              "{} {} {}\n".format(
                  self._num_nodes, self._num_nodes, self._num_edges
              )
          )
          for u in self._nodes:
              for v in self._neighbours[u]:
                  file.write("{} {}\n".format(u + 1, v + 1))
  
file_path: AutoGL/autogl/module/_feature/generators/graphlet.py
imports: import numpy
  import copy
  from .base import BaseGenerator
  from tqdm import tqdm
  from ....utils import get_logger
  from ..None import register_feature
label_desc: Use image node_id 7 for calling the Graphlet obj's underlying member method code with example usage: obj._save(filename) without return types