human
I wrote the below code

    def decorator(func):
        def inner(self, operand, operand2=None, **kwargs):
            global _config_ccd_requires_unit
            _config_ccd_requires_unit = False
            result = self._prepare_then_do_arithmetic(op, operand, operand2, **kwargs)
            _config_ccd_requires_unit = True
            return result.__class__(result)
        inner.__doc__ = u'See    `astropy.nddata.NDArithmeticMixin.{}`.'.format(func.__name__)
        return sharedmethod(inner)
    return decorator

What's a good function header?
assistant
#Here's a good function header.

def _arithmetic(op):