docs: def downgrade():
      """Downgrade database."""
      op.drop_table('files_multipartobject_part')
      op.drop_index(op.f('ix_files_object__mimetype'), table_name='files_object')
      op.drop_table('files_object')
      op.drop_table('files_multipartobject')
      op.drop_table('files_buckettags')
      op.drop_table('files_bucket')
      op.drop_table('files_location')
      op.drop_table('files_files')