class_docstr: Abstract class for generating neighbors.
  
  This class is to be inherited by the class that actually implements the method
  to generate neighbors.
code: def gen_neighbor(self):
      raise NotImplementedError
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
label_desc: Use image node_id 2 for calling the GenNeighbor obj's underlying member method code with example usage: obj.gen_neighbor() without return types