def register_element_cls(tag, cls):
    nspfx, tagroot = tag.split(':')
    namespace = element_class_lookup.get_namespace(nsmap[nspfx])
    namespace[tagroot] = cls
Register *cls* to be constructed when the oxml parser encounters an
dataset/ETHPy150Open python-openxml/python-docx/docx/oxml/__init__.py/register_element_cls