docs: def upgrade():
      """Upgrade database."""
      op.create_table(
          'records_buckets',
          sa.Column(
              'record_id',
              sqlalchemy_utils.types.uuid.UUIDType(),
              nullable=False),
          sa.Column(
              'bucket_id',
              sqlalchemy_utils.types.uuid.UUIDType(),
              nullable=False),
          sa.ForeignKeyConstraint(['bucket_id'], [u'files_bucket.id'], ),
          sa.ForeignKeyConstraint(['record_id'], [u'records_metadata.id'], ),
          sa.PrimaryKeyConstraint('record_id', 'bucket_id')
      )