'Returns whether the number is not actually one.
if self, other are sNaN, signal
if self, other are NaN return nan
return 0
Done before operations.'

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

    self_is_nan = self._isnan()
    if (other is None):
        other_is_nan = False
    else:
        other_is_nan = other._isnan()
    if (self_is_nan or other_is_nan):
        if (context is None):
            context = getcontext()
        if (self_is_nan == 2):
            return context._raise_error(InvalidOperation, 'sNaN', self)
        if (other_is_nan == 2):
            return context._raise_error(InvalidOperation, 'sNaN', other)
        if self_is_nan:
            return self._fix_nan(context)
        return other._fix_nan(context)
    return 0
