def _call(self, x, out=None):
        """Take the power of ``x`` and write to ``out`` if given."""
        if out is None:
            return x ** self.exponent
        elif self.__domain_is_field:
            raise ValueError('cannot use `out` with field')
        else:
            out.assign(x)
            out **= self.exponent
def _call ( self , x , out = None ) : if out is None : return x ** self . exponent elif self . __domain_is_field : raise ValueError ( 'cannot use `out` with field' ) else : out . assign ( x ) out **= self . exponent
Take the power of ``x`` and write to ``out`` if given.