code: def delete_unnecessary_constant_nodes(tfssa):
      delete_count = delete_nodes_with_only_constant_descendents(tfssa)
      for f in list(tfssa.functions.values()):
          check_connections(f.graph)
      convert_constant_nodes_to_const_ops(tfssa)
      logging.debug("%s nodes deleted", delete_count)
      return delete_count
  
imports: from __future__ import print_function
  from __future__ import division
  from __future__ import absolute_import
  from ..basic_graph_ops import delete_node, check_connections, disconnect_edge
  import logging
label_desc: Use image node_id 3 for calling a global function with example usage: delete_unnecessary_constant_nodes(tfssa) and returns: delete_count