class_docstr: GraphItem is a TensorFlow Graph wrapper.
  
  It represents the states in-between consecutive AutoDist.kernel graph transformations.
  tf.Graph is the primary property of GraphItem, whereas MetaGraph is exported/generated on demand.
  
  A GraphItem can be constructed with either a `tf.Graph` or a `GraphDef`.
docstr: Serialize a graph_item to a specific proto string down to a file path.
docstr_tok: ["Serialize","a","graph_item","to","a","specific","proto","string","down","to","a","file","path","."]
code: def serialize(self, path):
      """Serialize a graph_item to a specific proto string down to a file path."""
      item_def = graphitem_pb2.GraphItem()
      # GraphDef
      item_def.graph_def.Pack(self.graph.as_graph_def())
      # Grad Target Pairs
      for k, v in self._grad_target_pairs.items():
          if isinstance(k, tuple):
              k = ";".join(k)
          item_def.grad_target_pairs[k] = v
  
      # Info
      def f(v, repeated_any):
          a = Any()
          a.Pack(v)
          repeated_any.append(a)
  
      for v in self.info.variables:
          f(v, item_def.info.variables)
      for v in self.info.savers:
          f(v, item_def.info.savers)
      item_def.info.table_initializers.extend(
          self.info.table_initializers
      )
      logging.warning(
          "GraphItem currently does not serialize optimizer info, "
          "while optimizer info is only temporarily used for partitioner."
      )
      # Serialization
      item_def.SerializeToString()
      with open(path, "wb+") as f:
          f.write(item_def.SerializeToString())
  
imports: import contextlib
  import copy
  import functools
  from collections import defaultdict
  from typing import Union, Callable
  from google.protobuf.any_pb2 import Any
  from tensorflow.core.framework.graph_pb2 import GraphDef
  from tensorflow.core.framework.variable_pb2 import VariableDef
  from tensorflow.core.protobuf.saver_pb2 import SaverDef
  from tensorflow.python.framework import ops
  from tensorflow.python.framework.importer import import_graph_def
  from tensorflow.python.ops.resource_variable_ops import _from_proto_fn
  from tensorflow.python.ops.variables import Variable
  from autodist.const import COLOCATION_PREFIX
  from autodist.kernel.common import op_info
  from autodist.kernel.common.utils import parse_name_scope, get_op_name
  from autodist.proto import graphitem_pb2
  from autodist.utils import logging
label_desc: Use image node_id 23 for calling the GraphItem obj's underlying member method code with example usage: obj.serialize(path) without return types