code: def _num_file_lines(self, graph_path):
      with open(graph_path, "r") as f:
          return sum(1 for _ in f)
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import cmath
  from absl.testing import absltest
  from neural_structured_learning.tools import build_graph
  from neural_structured_learning.tools import graph_utils
  import six
  import tensorflow
  from google.protobuf import text_format
label_desc: Use image node_id 3 for calling the BuildGraphTest obj's underlying member method code with example usage: obj._num_file_lines(graph_path) and returns: sum