class_docstr: No transaction batch to write large number of entities.
  
  Usage:
    client = ...  # instance of CompetitionDatastoreClient
    with NoTransactionBatch(client) as batch:
      batch.put(entity1)
      ...
      batch.put(entityN)
      batch.delete(del_entity1)
      ...
      batch.delete(del_entityM)
  
  It could be also used via CompetitionDatastoreClient.no_transact_batch:
    client = ...  # instance of CompetitionDatastoreClient
    with client.no_transact_batch() as batch:
      batch.put(entity1)
      ...
      batch.put(entityN)
      batch.delete(del_entity1)
      ...
      batch.delete(del_entityM)
  
  Most methods of this class are provided to simulate
  google.cloud.datastore.batch.Batch interface, so they could be used
  interchangeably.
  Practically speaking, this class works by maintaining a buffer of
  pending mutations and committing them as soon as the length of the buffer
  reaches MAX_MUTATIONS_IN_BATCH.
docstr: Adds deletion of the entity with given key to the mutation buffer.
  
  If mutation buffer reaches its capacity then this method commit all pending
  mutations from the buffer and emties it.
  
  Args:
    key: key of the entity which should be deleted
docstr_tok: ["Adds","deletion","of","the","entity","with","given","key","to","the","mutation","buffer",".","If","mutation","buffer","reaches","its","capacity","then","this","method","commit","all","pending","mutations","from","the","buffer","and","emties","it",".","Args",":","key",":","key","of","the","entity","which","should","be","deleted"]
code: def delete(self, key):
      """Adds deletion of the entity with given key to the mutation buffer.
  
      If mutation buffer reaches its capacity then this method commit all pending
      mutations from the buffer and emties it.
  
      Args:
        key: key of the entity which should be deleted
      """
      self._cur_batch.delete(key)
      self._num_mutations += 1
      if self._num_mutations >= MAX_MUTATIONS_IN_BATCH:
          self.commit()
          self.begin()
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import logging
  import math
  import random
  import time
  import traceback
  from google.cloud import datastore
  from google.cloud import storage
  from google.cloud.exceptions import TooManyRequests
label_desc: Use image node_id 6 for calling the NoTransactionBatch obj's underlying member method code with example usage: obj.delete(key) without return types