code: def find_placeholders(grads):
      import tensorflow as tf
  
      def predicate(t):
          if not isinstance(t, tf.Operation):
              return t.op.type.startswith("Placeholder")
          else:
              return False
  
      return find_tensors(grads, predicate)
  
imports: import sys
  import warnings
  from bigdl.dllib.utils.log4Error import *
label_desc: Use image node_id 2 for calling a global function with example usage: find_placeholders(grads) and returns: find_tensors, t, False