Python orderedContent PyXB返回空列表

我正在尝试使用pyxb库解析简单和复杂类型的XML文件。以下是XML结构：

            </Requirement>
            <Section name="Electrical Characteristics">                     
            </Section>
        </Section>
    </Source>
</Requirements>

            <Section name="Electrical Characteristics">                     
            </Section>

            </Requirement>
            <Section name="Electrical Characteristics">                     
            </Section>
        </Section>
    </Source>
</Requirements>

            <Section name="Electrical Characteristics">                     
            </Section>

我在

ordered\u实例

变量中得到空列表

            </Requirement>
            <Section name="Electrical Characteristics">                     
            </Section>
        </Section>
    </Source>
</Requirements>

            <Section name="Electrical Characteristics">                     
            </Section>