def operation(self, operation_name, val):
        print('OPERATION: {} ... {}'.format(operation_name, val))
        if self.props['operations'] not in operation_name:
            raise ValueError(
                'Operation {} does not exist!'.format(operation_name))
        _args, _kwargs = val['args'], val['kwargs']
        return self.props['operations'][operation_name](*_args, **_kwargs)


# These constraints and operations are laid bare and can be used in classes,
# etc, as pure-ish functions.

# Operations
dataset/ETHPy150Open christabor/MoAL/MOAL/storage/modeling/data_modeling.py/Structure.operation/swapped operands of `not in`