code: def _build_activation_vars(self, input_act_vars):
      return tf.nn.sigmoid(input_act_vars)
  
imports: from __future__ import division
  from __future__ import print_function
  from __future__ import absolute_import
  from .core import SingleInputMixin, OneDimOutputMixin, Node, ScoringMode, NonlinearMxtsMode
  import tensorflow
  from deeplift.util import NEAR_ZERO_THRESHOLD
  from deeplift.layers import helper_functions
label_desc: Use image node_id 1 for calling the Sigmoid obj's underlying member method code with example usage: obj._build_activation_vars(input_act_vars) and returns: tf