Loads all the child line elements from the XML group element.

def _load(self, element, commentchar):
        """Loads all the child line elements from the XML group element."""
        for child in element:            
            if "id" in child.attrib:
                tline = TemplateLine(child, self, commentchar)
                self.order.append(tline.identifier)
                self.lines[tline.identifier] = tline
            else:
                msg.warn("no id element in {}. Ignored. (group._load)".format(child))