Reads an xml object from the stream.

        @return: An etree interface compatible object
        @see: L{xml.set_default_interface}

def readXML(self):
        """
        Reads an xml object from the stream.

        @return: An etree interface compatible object
        @see: L{xml.set_default_interface}
        """
        ref = self.readInteger(False)

        if ref & REFERENCE_BIT == 0:
            return self.context.getObject(ref >> 1)

        xmlstring = self.stream.read(ref >> 1)

        x = xml.fromstring(xmlstring)
        self.context.addObject(x)

        return x