docstr: Overwrites TFLoader._tf_ssa_from_graph_def()
docstr_tok: ["Overwrites","TFLoader._tf_ssa_from_graph_def","(",")"]
code: def _tf_ssa_from_graph_def(self, fn_name="main"):
      """Overwrites TFLoader._tf_ssa_from_graph_def()"""
      with _tf.Graph().as_default() as tf_graph:
          _tf.graph_util.import_graph_def(self._graph_def, name="")
  
      # sub-graphs' input shapes are required for extracting sub-graphs
      sg_input_shapes = self._populate_sub_graph_input_shapes(
          tf_graph, tf_graph._functions
      )
  
      # get graph_dict and sub-graphs' inputs / outputs
      graph_dict, inputs, outputs, ret = self._dict_from_graph_def(
          tf_graph, fn_name, sg_input_shapes
      )
  
      tf_ssa = NetworkEnsemble()
      for name, graph in graph_dict.items():
          tensor_array_resource_removal(graph)
          graph = insert_get_tuple(graph)
          graph = fill_outputs(graph)
          if (
              name == "main"
          ):  # skip for sub-graphs as input can be also output
              delete_disconnected_nodes(graph)
          tf_ssa.functions[name] = SSAFunction(
              graph,
              inputs=inputs[name],
              outputs=outputs[name],
              ret=ret[name],
          )
  
      return tf_ssa
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import logging
  import os.path
  from six import string_types
  from tqdm import tqdm
  import tensorflow
  from tensorflow.python.framework import dtypes
  from tensorflow.python.framework.convert_to_constants import convert_variables_to_constants_v2
  from tensorflow.python.framework.function_def_to_graph import function_def_to_graph
  from tensorflow.python.keras.saving import saving_utils
  from tensorflow.lite.python.util import run_graph_optimizations
  from tensorflow.lite.python.util import get_grappler_config
  from .converter import TF2Converter
  from coremltools.converters.mil.frontend.tensorflow.basic_graph_ops import fill_outputs
  from coremltools.converters.mil.frontend.tensorflow.tf_graph_pass import constant_propagation, remove_variable_nodes, tensor_array_resource_removal, insert_get_tuple, delete_disconnected_nodes, fuse_dilation_conv
  from coremltools.converters.mil.frontend.tensorflow2.tf_graph_pass import flatten_sub_graph_namespaces, rewrite_control_flow_functions
  from coremltools.converters.mil.frontend.tensorflow.tfssa import NetworkEnsemble, SSAFunction
  from coremltools.converters.mil.frontend.tensorflow.parsed_tf_node import ParsedTFNode
  from coremltools.converters.mil.frontend.tensorflow.load import TFLoader
label_desc: Use image node_id 3 for calling the TF2Loader obj's underlying member method code with example usage: obj._tf_ssa_from_graph_def(fn_name) and returns: tf_ssa