class_docstr: Sign activation function.
  Computes the function f(x) = Sign(x).
  Uses straight-through estimator for bprop.
code: def __init__(self, name=None):
      super(Sign, self).__init__(name)
  
imports: from __future__ import division
  from neon.transforms.transform import Transform
label_desc: Use image node_id 1 to create a new Sign object from inherited base classes: Transform with example: obj = Sign(name)