AttributeError：_ElementInterface实例没有属性＆＃39; iter＆＃39;

Question

我正在尝试使用Python迭代XML文件。这是一段代码：

for fields in root.iter('context'):
        for ID in fields.iter('ID'):
            try:
                name = ID.attrib['name']
                if name in fields_to_remove:
                    removed.append({'name': name, 'tag': ID})
            except KeyError:
                pass
        if removed:
            comment = ','.join([ ID['name'] for ID in removed])
            for ID in removed:
                fields.remove(ID['tag'])
            fields.append(ET.Comment('Removed ' + comment))
            removed = []

XML示例：

<context name="Subscription" category="subscription" type="generic" optimizeSize="1">
                <field name="DELTA_MID_RT" type="bool" id="-1" defaultValue="false"/>
                <field name="API::TZO" type="int32" id="-1" defaultValue="0"/>
                <field name="API::DIVIDENTADJUST" type="bool" id="-1"/>

        </context>

错误讯息：

Traceback (most recent call last):
  File "parser.py", line 20, in <module>
    for fields in root.iter('context'):
AttributeError: _ElementInterface instance has no attribute 'iter'