import tensorflow as tf


                vx = tf.contrib.lookup.MutableHashTable(key_dtype=tf.string,
                                                        value_dtype=tf.int64,
                                                        default_value=-1)

                vz = tf.contrib.lookup.MutableHashTable(key_dtype=tf.string,
                                                        value_dtype=tf.int64,
                                                        default_value=-1)

                vx_keys = tf.reshape(tf.Variable([], collections=[], dtype=tf.string), (-1, 1))
