'Return self - other'

def __sub__(self, other, context=None):

    other = _convert_other(other)
    if (other is NotImplemented):
        return other
    if (self._is_special or other._is_special):
        ans = self._check_nans(other, context=context)
        if ans:
            return ans
    return self.__add__(other.copy_negate(), context=context)
