code: def get_tensor_parents_placeholders(tensor):
      """Get all placeholders that is depending the given tensor."""
      placeholders_list = []
      if tensor.op.type == "Placeholder":
          placeholders_list.append(tensor)
      if tensor.op:
          for t in tensor.op.inputs:
              if not "read:0" in t.name:
                  placeholders_list += get_tensor_parents_placeholders(
                      t
                  )
      return list(set(placeholders_list))
  
imports: from __future__ import division, print_function, absolute_import
  import six
  import string
  import random
  import numpy
  import tensorflow.compat.v1
  from tensorflow.python import pywrap_tensorflow
  import tflearn.variables
label_desc: Use image node_id 4 for calling a global function with example usage: get_tensor_parents_placeholders(tensor) and returns: list