class_docstr: Fake for datastore transaction.
  
  See https://cloud.google.com/datastore/docs/concepts/transactions
  for details of how transactions work in Cloud Datastore.
class_docstr_tok: ["Fake","for","datastore","transaction",".","See","https",":","\/\/cloud.google.com\/datastore\/docs\/concepts\/transactions","for","details","of","how","transactions","work","in","Cloud","Datastore","."]
docstr: Rolls back current transaction.
docstr_tok: ["Rolls","back","current","transaction","."]
code: def rollback(self):
      """Rolls back current transaction."""
      self._check_update_state("started", "rolledback")
      self._mutations = []
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  import copy
  from io import StringIO
  import six
label_desc: Use image node_id 6 for calling the FakeDatastoreClientTransaction obj's underlying member method code with example usage: obj.rollback() without return types