class_docstr: Attention layer according to https://arxiv.org/abs/1409.0473.
  
  Params:
    num_units: Number of units used in the attention layer
docstr: Computes the attention score
docstr_tok: ["Computes","the","attention","score"]
code: def score_fn(self, keys, query):
      """Computes the attention score"""
      raise NotImplementedError
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from __future__ import unicode_literals
  import abc
  import six
  import tensorflow
  from tensorflow.python.framework import function
  from seq2seq.graph_module import GraphModule
  from seq2seq.configurable import Configurable
label_desc: Use image node_id 3 for calling the AttentionLayer obj's underlying member method code with example usage: obj.score_fn(keys, query) without return types