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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def to_element(self, root_name=None):
 """Serialize this `Resource` instance to an XML element."""

        if not root_name:
            root_name = self.nodename
        elem = ElementTreeBuilder.Element(root_name)
        for attrname in self.serializable_attributes():
            # Only use values that have been loaded into the internal
            # __dict__. For retrieved objects we look into the XML response at
            # access time, so the internal __dict__ contains only the elements
            # that have been set on the client side.
            try:
                value = self.__dict__[attrname]
            except KeyError:
                continue

            if attrname in self.xml_attribute_attributes:
                elem.attrib[attrname] = six.text_type(value)
            else:
                sub_elem = self.element_for_value(attrname, value)
                elem.append(sub_elem)

        return elem