text: # coding: utf-8
  #
  # Copyright 2014 The Oppia Authors. All Rights Reserved.
  #
  # Licensed under the Apache License, Version 2.0 (the "License");
  # you may not use this file except in compliance with the License.
  # You may obtain a copy of the License at
  #
  #      http://www.apache.org/licenses/LICENSE-2.0
  #
  # Unless required by applicable law or agreed to in writing, software
  # distributed under the License is distributed on an "AS-IS" BASIS,
  # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  # See the License for the specific language governing permissions and
  # limitations under the License.
  
  """Model for an Oppia exploration."""
  from __future__ import absolute_import  # pylint: disable=import-only-modules
  from __future__ import unicode_literals  # pylint: disable=import-only-modules
  
  import datetime
  
  from constants import constants
  import core.storage.base_model.gae_models as base_models
  import core.storage.user.gae_models as user_models
  import feconf
  
  from google.appengine.ext import ndb
  
  
  class ExplorationSnapshotMetadataModel(base_models.BaseSnapshotMetadataModel):
      """Storage model for the metadata for an exploration snapshot."""
      pass
  
  
  class ExplorationSnapshotContentModel(base_models.BaseSnapshotContentModel):
      """Storage model for the content of an exploration snapshot."""
      pass
  
  
  class ExplorationModel(base_models.VersionedModel):
      """Versioned storage model for an Oppia exploration.
  
      This class should only be imported by the exploration services file
      and the exploration model test file.
      """
      SNAPSHOT_METADATA_CLASS = ExplorationSnapshotMetadataModel
      SNAPSHOT_CONTENT_CLASS = ExplorationSnapshotContentModel
      ALLOW_REVERT = True
  
      # What this exploration is called.
      title = ndb.StringProperty(required=True)
      # The category this exploration belongs to.
      category = ndb.StringProperty(required=True, indexed=True)
      # The objective of this exploration.
      objective = ndb.TextProperty(default='', indexed=False)
      # The ISO 639-1 code for the language this exploration is written in.
      language_code = ndb.StringProperty(
          default=constants.DEFAULT_LANGUAGE_CODE, indexed=True)
      # Tags (topics, skills, concepts, etc.) associated with this
      # exploration.
      tags = ndb.StringProperty(repeated=True, indexed=True)
      # A blurb for this exploration.
      blurb = ndb.TextProperty(default='', indexed=False)
      # 'Author notes' for this exploration.
      author_notes = ndb.TextProperty(default='', indexed=False)
  
      # The version of the states blob schema.
      states_schema_version = ndb.IntegerProperty(
          required=True, default=0, indexed=True)
      # The name of the initial state of this exploration.
      init_state_name = ndb.StringProperty(required=True, indexed=False)
      # A dict representing the states of this exploration. This dict should
      # not be empty.
      states = ndb.JsonProperty(default={}, indexed=False)
      # The dict of parameter specifications associated with this exploration.
      # Each specification is a dict whose keys are param names and whose values
      # are each dicts with a single key, 'obj_type', whose value is a string.
      param_specs = ndb.JsonProperty(default={}, indexed=False)
      # The list of parameter changes to be performed once at the start of a
      # reader's encounter with an exploration.
      param_changes = ndb.JsonProperty(repeated=True, indexed=False)
      # A boolean indicating whether automatic text-to-speech is enabled in
      # this exploration.
      auto_tts_enabled = ndb.BooleanProperty(default=True, indexed=True)
      # A boolean indicating whether correctness feedback is enabled in this
      # exploration.
      correctness_feedback_enabled = ndb.BooleanProperty(
          default=False, indexed=True)
  
      # DEPRECATED in v2.0.0.rc.2. Do not use. Retaining it here because deletion
      # caused GAE to raise an error on fetching a specific version of the
      # exploration model.
      # TODO(sll): Fix this error and remove this property.
      skill_tags = ndb.StringProperty(repeated=True, indexed=True)
      # DEPRECATED in v2.0.1. Do not use.
      # TODO(sll): Remove this property from the model.
      default_skin = ndb.StringProperty(default='conversation_v1')
      # DEPRECATED in v2.5.4. Do not use.
      skin_customizations = ndb.JsonProperty(indexed=False)
  
      @staticmethod
      def get_deletion_policy():
          """Exploration is deleted only if it is not public."""
          return base_models.DELETION_POLICY.KEEP_IF_PUBLIC
  
      @classmethod
      def get_exploration_count(cls):
          """Returns the total number of explorations."""
          return cls.get_all().count()
  
      def _trusted_commit(
              self, committer_id, commit_type, commit_message, commit_cmds):
          """Record the event to the commit log after the model commit.
  
          Note that this extends the superclass method.
  
          Args:
              committer_id: str. The user_id of the user who committed the
                  change.
              commit_type: str. The type of commit. Possible values are in
                  core.storage.base_models.COMMIT_TYPE_CHOICES.
              commit_message: str. The commit description message.
              commit_cmds: list(dict). A list of commands, describing changes
                  made in this model, which should give sufficient information to
                  reconstruct the commit. Each dict always contains:
                      cmd: str. Unique command.
                  and then additional arguments for that command.
          """
          super(ExplorationModel, self)._trusted_commit(
              committer_id, commit_type, commit_message, commit_cmds)
  
          committer_user_settings_model = (
              user_models.UserSettingsModel.get_by_id(committer_id))
          committer_username = (
              committer_user_settings_model.username
              if committer_user_settings_model else '')
  
          exp_rights = ExplorationRightsModel.get_by_id(self.id)
  
          # TODO(msl): test if put_async() leads to any problems (make
          # sure summary dicts get updated correctly when explorations
          # are changed).
          exploration_commit_log = ExplorationCommitLogEntryModel.create(
              self.id, self.version, committer_id, committer_username,
              commit_type, commit_message, commit_cmds, exp_rights.status,
              exp_rights.community_owned
          )
          exploration_commit_log.exploration_id = self.id
          exploration_commit_log.put()
  
  
  class ExplorationRightsSnapshotMetadataModel(
          base_models.BaseSnapshotMetadataModel):
      """Storage model for the metadata for an exploration rights snapshot."""
      pass
  
  
  class ExplorationRightsSnapshotContentModel(
          base_models.BaseSnapshotContentModel):
      """Storage model for the content of an exploration rights snapshot."""
      pass
  
  
  class ExplorationRightsModel(base_models.VersionedModel):
      """Storage model for rights related to an exploration.
  
      The id of each instance is the id of the corresponding exploration.
      """
  
      SNAPSHOT_METADATA_CLASS = ExplorationRightsSnapshotMetadataModel
      SNAPSHOT_CONTENT_CLASS = ExplorationRightsSnapshotContentModel
      ALLOW_REVERT = False
  
      # The user_ids of owners of this exploration.
      owner_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who are allowed to edit this exploration.
      editor_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who are allowed to voiceover this exploration.
      voice_artist_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who are allowed to view this exploration.
      viewer_ids = ndb.StringProperty(indexed=True, repeated=True)
  
      # Whether this exploration is owned by the community.
      community_owned = ndb.BooleanProperty(indexed=True, default=False)
      # The exploration id which this exploration was cloned from. If None, this
      # exploration was created from scratch.
      cloned_from = ndb.StringProperty()
      # For private explorations, whether this exploration can be viewed
      # by anyone who has the URL. If the exploration is not private, this
      # setting is ignored.
      viewable_if_private = ndb.BooleanProperty(indexed=True, default=False)
      # Time, in milliseconds, when the exploration was first published.
      first_published_msec = ndb.FloatProperty(indexed=True, default=None)
  
      # The publication status of this exploration.
      status = ndb.StringProperty(
          default=constants.ACTIVITY_STATUS_PRIVATE, indexed=True,
          choices=[
              constants.ACTIVITY_STATUS_PRIVATE,
              constants.ACTIVITY_STATUS_PUBLIC
          ]
      )
      # DEPRECATED in v2.8.3. Do not use.
      translator_ids = ndb.StringProperty(indexed=True, repeated=True)
  
      @staticmethod
      def get_deletion_policy():
          """Exploration rights are deleted only if the corresponding exploration
          is not public.
          """
          return base_models.DELETION_POLICY.KEEP_IF_PUBLIC
  
      def save(self, committer_id, commit_message, commit_cmds):
          """Saves a new version of the exploration, updating the Exploration
          datastore model.
  
          Args:
              committer_id: str. The user_id of the user who committed the
                  change.
              commit_message: str. The commit description message.
              commit_cmds: list(dict). A list of commands, describing changes
                  made in this model, which should give sufficient information to
                  reconstruct the commit. Each dict always contains:
                      cmd: str. The type of the command. A full list of command
                          types can be found in core/domain/exp_domain.py.
                  and then additional arguments for that command. For example:
  
                  {'cmd': 'AUTO_revert_version_number',
                   'version_number': 4}
          """
          super(ExplorationRightsModel, self).commit(
              committer_id, commit_message, commit_cmds)
  
      def _trusted_commit(
              self, committer_id, commit_type, commit_message, commit_cmds):
          """Record the event to the commit log after the model commit.
  
          Note that this extends the superclass method.
  
          Args:
              committer_id: str. The user_id of the user who committed the
                  change.
              commit_type: str. The type of commit. Possible values are in
                  core.storage.base_models.COMMIT_TYPE_CHOICES.
              commit_message: str. The commit description message.
              commit_cmds: list(dict). A list of commands, describing changes
                  made in this model, should give sufficient information to
                  reconstruct the commit. Each dict always contains:
                      cmd: str. Unique command.
                  and then additional arguments for that command.
          """
          super(ExplorationRightsModel, self)._trusted_commit(
              committer_id, commit_type, commit_message, commit_cmds)
  
          # Create and delete events will already be recorded in the
          # ExplorationModel.
          if commit_type not in ['create', 'delete']:
              committer_user_settings_model = (
                  user_models.UserSettingsModel.get_by_id(committer_id))
              committer_username = (
                  committer_user_settings_model.username
                  if committer_user_settings_model else '')
              # TODO(msl): test if put_async() leads to any problems (make
              # sure summary dicts get updated correctly when explorations
              # are changed).
              ExplorationCommitLogEntryModel(
                  id=('rights-%s-%s' % (self.id, self.version)),
                  user_id=committer_id,
                  username=committer_username,
                  exploration_id=self.id,
                  commit_type=commit_type,
                  commit_message=commit_message,
                  commit_cmds=commit_cmds,
                  version=None,
                  post_commit_status=self.status,
                  post_commit_community_owned=self.community_owned,
                  post_commit_is_private=(
                      self.status == constants.ACTIVITY_STATUS_PRIVATE)
              ).put_async()
  
      @classmethod
      def export_data(cls, user_id):
          """(Takeout) Export user-relevant properties of ExplorationRightsModel.
  
          Args:
              user_id: str. The user_id denotes which user's data to extract.
  
          Returns:
              dict or None. The user-relevant properties of ExplorationRightsModel
              in a python dict format. In this case, we are returning all the
              ids of explorations that the user is connected to, so they either
              own, edit, voice, or have permission to view.
          """
          owned_explorations = cls.get_all().filter(cls.owner_ids == user_id)
          editable_explorations = cls.get_all().filter(cls.editor_ids == user_id)
          voiced_explorations = (
              cls.get_all().filter(cls.voice_artist_ids == user_id))
          viewable_explorations = cls.get_all().filter(cls.viewer_ids == user_id)
  
          owned_exploration_ids = [exp.key.id() for exp in owned_explorations]
          editable_exploration_ids = (
              [exp.key.id() for exp in editable_explorations])
          voiced_exploration_ids = [exp.key.id() for exp in voiced_explorations]
          viewable_exploration_ids = (
              [exp.key.id() for exp in viewable_explorations])
  
          return {
              'owned_exploration_ids': owned_exploration_ids,
              'editable_exploration_ids': editable_exploration_ids,
              'voiced_exploration_ids': voiced_exploration_ids,
              'viewable_exploration_ids': viewable_exploration_ids
          }
  
  
  class ExplorationCommitLogEntryModel(base_models.BaseCommitLogEntryModel):
      """Log of commits to explorations.
  
      A new instance of this model is created and saved every time a commit to
      ExplorationModel or ExplorationRightsModel occurs.
  
      The id for this model is of the form
      'exploration-{{EXP_ID}}-{{EXP_VERSION}}'.
      """
      # The id of the exploration being edited.
      exploration_id = ndb.StringProperty(indexed=True, required=True)
  
      @classmethod
      def get_multi(cls, exp_id, exp_versions):
          """Gets the ExplorationCommitLogEntryModels for the given exploration
          id and exploration versions.
  
          Args:
              exp_id: str. The id of the exploration.
              exp_versions: list(int). The versions of the exploration.
  
          Returns:
              list(ExplorationCommitLogEntryModel). The list of
              ExplorationCommitLogEntryModel instances which matches the given
              exp_id and exp_versions.
          """
          instance_ids = [cls._get_instance_id(exp_id, exp_version)
                          for exp_version in exp_versions]
  
          return super(ExplorationCommitLogEntryModel, cls).get_multi(
              instance_ids)
  
      @classmethod
      def _get_instance_id(cls, exp_id, exp_version):
          """Returns ID of the exploration commit log entry model.
  
          Args:
              exp_id: str. The exploration id whose states are mapped.
              exp_version: int. The version of the exploration.
  
          Returns:
              str. A string containing exploration ID and
                  exploration version.
          """
          return 'exploration-%s-%s' % (exp_id, exp_version)
  
      @classmethod
      def get_all_non_private_commits(
              cls, page_size, urlsafe_start_cursor, max_age=None):
          """Fetches a list of all the non-private commits sorted by their
          last updated attribute.
  
          Args:
              page_size: int. The maximum number of entities to be returned.
              urlsafe_start_cursor: str or None. If provided, the list of
                  returned entities starts from this datastore cursor.
                  Otherwise, the returned entities start from the beginning
                  of the full list of entities.
              max_age: datetime.timedelta. The maximum time duration within which
                  commits are needed.
  
          Returns:
              3-tuple of (results, cursor, more) which were created which were
              created no earlier than max_age before the current time where:
                  results: List of query results.
                  cursor: str or None. A query cursor pointing to the next
                      batch of results. If there are no more results, this will
                      be None.
                  more: bool. If True, there are (probably) more results after
                      this batch. If False, there are no further results after
                      this batch.
          """
  
          if not isinstance(max_age, datetime.timedelta) and max_age is not None:
              raise ValueError(
                  'max_age must be a datetime.timedelta instance or None.')
  
          query = cls.query(cls.post_commit_is_private == False)  # pylint: disable=singleton-comparison
          if max_age:
              query = query.filter(
                  cls.last_updated >= datetime.datetime.utcnow() - max_age)
          return cls._fetch_page_sorted_by_last_updated(
              query, page_size, urlsafe_start_cursor)
  
  
  class ExpSummaryModel(base_models.BaseModel):
      """Summary model for an Oppia exploration.
  
      This should be used whenever the content blob of the exploration is not
      needed (e.g. in search results, etc).
  
      A ExpSummaryModel instance stores the following information:
  
          id, title, category, objective, language_code, tags,
          last_updated, created_on, status (private, public),
          community_owned, owner_ids, editor_ids,
          viewer_ids, version.
  
      The key of each instance is the exploration id.
      """
  
      # What this exploration is called.
      title = ndb.StringProperty(required=True)
      # The category this exploration belongs to.
      category = ndb.StringProperty(required=True, indexed=True)
      # The objective of this exploration.
      objective = ndb.TextProperty(required=True, indexed=False)
      # The ISO 639-1 code for the language this exploration is written in.
      language_code = ndb.StringProperty(required=True, indexed=True)
      # Tags associated with this exploration.
      tags = ndb.StringProperty(repeated=True, indexed=True)
  
      # Aggregate user-assigned ratings of the exploration.
      ratings = ndb.JsonProperty(default=None, indexed=False)
  
      # Scaled average rating for the exploration.
      scaled_average_rating = ndb.FloatProperty(indexed=True)
  
      # Time when the exploration model was last updated (not to be
      # confused with last_updated, which is the time when the
      # exploration *summary* model was last updated).
      exploration_model_last_updated = ndb.DateTimeProperty(indexed=True)
      # Time when the exploration model was created (not to be confused
      # with created_on, which is the time when the exploration *summary*
      # model was created).
      exploration_model_created_on = ndb.DateTimeProperty(indexed=True)
      # Time when the exploration was first published.
      first_published_msec = ndb.FloatProperty(indexed=True)
  
      # The publication status of this exploration.
      status = ndb.StringProperty(
          default=constants.ACTIVITY_STATUS_PRIVATE, indexed=True,
          choices=[
              constants.ACTIVITY_STATUS_PRIVATE,
              constants.ACTIVITY_STATUS_PUBLIC
          ]
      )
  
      # Whether this exploration is owned by the community.
      community_owned = ndb.BooleanProperty(required=True, indexed=True)
  
      # The user_ids of owners of this exploration.
      owner_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who are allowed to edit this exploration.
      editor_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who are allowed to voiceover this exploration.
      voice_artist_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who are allowed to view this exploration.
      viewer_ids = ndb.StringProperty(indexed=True, repeated=True)
      # The user_ids of users who have contributed (humans who have made a
      # positive (not just a revert) change to the exploration's content).
      contributor_ids = ndb.StringProperty(indexed=True, repeated=True)
      # A dict representing the contributors of non-trivial commits to this
      # exploration. Each key of this dict is a user_id, and the corresponding
      # value is the number of non-trivial commits that the user has made.
      contributors_summary = ndb.JsonProperty(default={}, indexed=False)
      # The version number of the exploration after this commit. Only populated
      # for commits to an exploration (as opposed to its rights, etc.).
      version = ndb.IntegerProperty()
      # DEPRECATED in v2.8.3. Do not use.
      translator_ids = ndb.StringProperty(indexed=True, repeated=True)
  
      @staticmethod
      def get_deletion_policy():
          """Exploration summary is deleted only if the corresponding exploration
          is not public.
          """
          return base_models.DELETION_POLICY.KEEP_IF_PUBLIC
  
      @classmethod
      def get_non_private(cls):
          """Returns an iterable with non-private ExpSummary models.
  
          Returns:
              iterable. An iterable with non-private ExpSummary models.
          """
          return ExpSummaryModel.query().filter(
              ExpSummaryModel.status != constants.ACTIVITY_STATUS_PRIVATE
          ).filter(
              ExpSummaryModel.deleted == False  # pylint: disable=singleton-comparison
          ).fetch(feconf.DEFAULT_QUERY_LIMIT)
  
      @classmethod
      def get_top_rated(cls, limit):
          """Fetches the top-rated exp summaries that are public in descending
          order of scaled_average_rating.
  
          Args:
              limit: int. The maximum number of results to return.
  
          Returns:
              iterable. An iterable with the top rated exp summaries that are
                  public in descending order of scaled_average_rating.
          """
          return ExpSummaryModel.query().filter(
              ExpSummaryModel.status == constants.ACTIVITY_STATUS_PUBLIC
          ).filter(
              ExpSummaryModel.deleted == False  # pylint: disable=singleton-comparison
          ).order(
              -ExpSummaryModel.scaled_average_rating
          ).fetch(limit)
  
      @classmethod
      def get_private_at_least_viewable(cls, user_id):
          """Fetches private exp summaries that are at least viewable by the
          given user.
  
          Args:
              user_id: The id of the given user.
  
          Returns:
              iterable. An iterable with private exp summaries that are at least
                  viewable by the given user.
          """
          return ExpSummaryModel.query().filter(
              ExpSummaryModel.status == constants.ACTIVITY_STATUS_PRIVATE
          ).filter(
              ndb.OR(ExpSummaryModel.owner_ids == user_id,
                     ExpSummaryModel.editor_ids == user_id,
                     ExpSummaryModel.voice_artist_ids == user_id,
                     ExpSummaryModel.viewer_ids == user_id)
          ).filter(
              ExpSummaryModel.deleted == False  # pylint: disable=singleton-comparison
          ).fetch(feconf.DEFAULT_QUERY_LIMIT)
  
      @classmethod
      def get_at_least_editable(cls, user_id):
          """Fetches exp summaries that are at least editable by the given user.
  
          Args:
              user_id: The id of the given user.
  
          Returns:
              iterable. An iterable with exp summaries that are at least
                  editable by the given user.
          """
          return ExpSummaryModel.query().filter(
              ndb.OR(ExpSummaryModel.owner_ids == user_id,
                     ExpSummaryModel.editor_ids == user_id)
          ).filter(
              ExpSummaryModel.deleted == False  # pylint: disable=singleton-comparison
          ).fetch(feconf.DEFAULT_QUERY_LIMIT)
  
      @classmethod
      def get_recently_published(cls, limit):
          """Fetches exp summaries that are recently published.
  
          Args:
              limit: int. The maximum number of results to return.
  
          Returns:
              An iterable with exp summaries that are recently published. The
                  returned list is sorted by the time of publication with latest
                  being first in the list.
          """
          return ExpSummaryModel.query().filter(
              ExpSummaryModel.status == constants.ACTIVITY_STATUS_PUBLIC
          ).filter(
              ExpSummaryModel.deleted == False  # pylint: disable=singleton-comparison
          ).order(
              -ExpSummaryModel.first_published_msec
          ).fetch(limit)
  
  
  class StateIdMappingModel(base_models.BaseModel):
      """DEPRECATED: DO NOT USE.
      State ID model for Oppia explorations.
      This model maps each exploration version's state to a unique id.
      Note: use the state id only for derived data, but not for data that’s
      regarded as the source of truth, as the rules for assigning state id may
      change in future.
      The key of each instance is a combination of exploration id and version.
      """
  
      # The exploration id whose states are mapped.
      exploration_id = ndb.StringProperty(indexed=True, required=True)
  
      # The version of the exploration.
      exploration_version = ndb.IntegerProperty(indexed=True, required=True)
  
      # A dict which maps each state name to a unique id.
      state_names_to_ids = ndb.JsonProperty(required=True)
  
      # Latest state id that has been assigned to any of the states in any of
      # of the versions of given exploration. New state IDs should be assigned
      # from this value + 1.
      largest_state_id_used = ndb.IntegerProperty(indexed=True, required=True)
  
      @classmethod
      def create(
              cls, exp_id, exp_version, state_names_to_ids,
              largest_state_id_used, overwrite=False):
          """Creates a new instance of state id mapping model.
          Args:
              exp_id: str. The exploration id whose states are mapped.
              exp_version: int. The version of that exploration.
              state_names_to_ids: dict. A dict storing state name to ids mapping.
              largest_state_id_used: int. The largest integer so far that has been
                  used as a state ID for this exploration.
              overwrite: bool. Whether overwriting of an existing model should
                  be allowed.
          Returns:
              StateIdMappingModel. Instance of the state id mapping model.
          """
          instance_id = cls._generate_instance_id(exp_id, exp_version)
          if not overwrite and cls.get_by_id(instance_id):
              raise Exception(
                  'State id mapping model already exists for exploration %s,'
                  ' version %d' % (exp_id, exp_version))
          model = cls(
              id=instance_id, exploration_id=exp_id,
              exploration_version=exp_version,
              state_names_to_ids=state_names_to_ids,
              largest_state_id_used=largest_state_id_used)
          model.put()
  
          return model
  
      @classmethod
      def _generate_instance_id(cls, exp_id, exp_version):
          """Generates ID of the state id mapping model instance.
          Args:
              exp_id: str. The exploration id whose states are mapped.
              exp_version: int. The version of the exploration.
          Returns:
              str. A string containing exploration ID and
                  exploration version.
          """
          return '%s.%d' % (exp_id, exp_version)
  
      @classmethod
      def get_state_id_mapping_model(cls, exp_id, exp_version):
          """Retrieve state id mapping model from the datastore.
          Args:
              exp_id: str. The exploration id.
              exp_version: int. The exploration version.
          Returns:
              StateIdMappingModel. The model retrieved from the datastore.
          """
          instance_id = cls._generate_instance_id(exp_id, exp_version)
          instance = cls.get(instance_id)
          return instance
  
      @classmethod
      def delete_state_id_mapping_models(cls, exp_id, exp_versions):
          """Removes state id mapping models present in state_id_mapping_models.
          Args:
              exp_id: str. The id of the exploration.
              exp_versions: list(int). A list of exploration versions for which
                  the state id mapping model is to be deleted.
          """
          keys = [
              ndb.Key(cls, cls._generate_instance_id(exp_id, exp_version))
              for exp_version in exp_versions]
          ndb.delete_multi(keys)
  