def __add__(self, other: Optional['FixedMetric']) -> 'FixedMetric':
    if (other is None):
        return self
    if (self != other):
        raise ValueError(f'FixedMetrics not the same: {self} and {other}')
    return self
def __add__(self, other: Optional['FixedMetric']) -> 'FixedMetric':
    if (other is None):
        return self
    if (self != other):
        raise ValueError(f'FixedMetrics not the same: {self} and {other}')
    return self