Returns an XMLi representation of the shipping details.
        @return: Element

def to_xml(self):
        '''
        Returns an XMLi representation of the shipping details.
        @return: Element
        '''
        for n, v in {"recipient": self.recipient}.items():
            if is_empty_or_none(v):
                raise ValueError("'%s' attribute cannot be empty or None." % n)

        doc = Document()
        root = doc.createElement("shipping")
        root.appendChild(self.recipient.to_xml("recipient"))
        return root