code: def remove_variable_node_impl(fn, tfssa):
      variables = [
          var for var in fn.graph.values() if var.op == "VariableV2"
      ]
      assigns = [
          assign
          for assign in fn.graph.values()
          if assign.op == "Assign"
      ]
      reads = [
          read
          for read in fn.graph.values()
          if read.op == "Identity"
          and len(read.inputs) == 1
          and fn.graph[read.inputs[0]].op == "VariableV2"
      ]
  
      # find the variable initial values
      variable_values = {}
      additional_nodes_to_delete = []
      for v in variables:
          v.parse_from_attr()
          variable_values[v.name] = v.datatype()
          for node in fn.graph.values():
              if (
                  node.op == "Assign"
                  and node.inputs[0] == v.name
                  and node.inputs[1] == v.name + "/initial_value"
              ):
                  variable_values[v.name] = fn.graph[
                      node.inputs[1]
                  ].value
                  additional_nodes_to_delete += [
                      node.name,
                      node.inputs[1],
                  ]
      for r in reads:
          r.op = "get_global"
          r.attr["variable"] = r.inputs[0]
          disconnect_vertex_ins(fn.graph, r.name)
  
      # transform writes to set_global
      for r in assigns:
          r.op = "set_global"
          r.attr["variable"] = r.inputs[0]
  
      for var in variables:
          delete_node(fn.graph, var.name)
  
      for node in additional_nodes_to_delete:
          delete_node(fn.graph, node)
  
      for k, v in variable_values.items():
          tfssa.variables[k] = v
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  from ..basic_graph_ops import disconnect_vertex_ins, delete_node
label_desc: Use image node_id 1 for calling a global function with example usage: remove_variable_node_impl(fn, tfssa) without return types