code: def get_operation_input_names(self, operation_name):
      
      for input_tensor in self._name_to_operation(operation_name).inputs:
        yield input_tensor.name
docs: Generates the names of all input tensors of an operation.
  
      Args:
        operation_name: a string, the name of an operation in the graph.
  
      Yields:
        a string, the name of an input tensor.