def delete_database(self, instance_id, database_id, project_id=None):
        """
        Drops a database in Cloud Spanner.

        :type project_id: str
        :param instance_id: The ID of the Cloud Spanner instance.
        :type instance_id: str
        :param database_id: The ID of the database in Cloud Spanner.
        :type database_id: str
        :param project_id: Optional, the ID of the  GCP project that owns the Cloud Spanner
            database. If set to None or missing, the default project_id from the GCP connection is used.
        :return: True if everything succeeded
        :rtype: bool
        """

        instance = self._get_client(project_id=project_id).\
            instance(instance_id=instance_id)
        if not instance.exists():
            raise AirflowException("The instance {} does not exist in project {} !".
                                   format(instance_id, project_id))
        database = instance.database(database_id=database_id)
        if not database.exists():
            self.log.info("The database {} is already deleted from instance {}. "
                          "Exiting.".format(database_id, instance_id))
            return
        try:
            operation = database.drop()  # type: Operation
        except GoogleAPICallError as e:
            self.log.error('An error occurred: %s. Exiting.', e.message)
            raise e

        if operation:
            result = operation.result()
            self.log.info(result)
        return
Drops a database in Cloud Spanner.

        :type project_id: str
        :param instance_id: The ID of the Cloud Spanner instance.
        :type instance_id: str
        :param database_id: The ID of the database in Cloud Spanner.
        :type database_id: str
        :param project_id: Optional, the ID of the  GCP project that owns the Cloud Spanner
            database. If set to None or missing, the default project_id from the GCP connection is used.
        :return: True if everything succeeded
        :rtype: bool