def METHOD_NAME(cls, classes: List[Class]):
    """
    Merge parent-child global types.
    Conditions
        1. One of them is derived from xs:element
        2. One of them is derived from xs:complexType
        3. The xs:element is a subclass of the xs:complexType
        4. The xs:element has no attributes (This can't happen in a valid schema)
    """
    el = collections.first(x for x in classes if x.tag == Tag.ELEMENT)
    ct = collections.first(x for x in classes if x.tag == Tag.COMPLEX_TYPE)
    if (
        el is None
        or ct is None
        or el is ct
        or el.attrs
        or len(el.extensions) != 1
        or el.extensions[0].type.qname != el.qname
    ):
        return
    ct.namespace = el.namespace or ct.namespace
    ct.help = el.help or ct.help
    ct.substitutions = el.substitutions
    classes.remove(el)