PyXB get order of sub-elements of arbitrary element type definition

Question

I'm working with multiple XSD class bindings using PyXB 1.2.6. I want to get the order of sub-element names of an arbitrary element type definition. So far I came up with this code:

from pyxb.binding.basis import element

def get_sub_elements(type_definition):
    """Returns an ordered list of the respective
    sub-elements of the given PyXB element.
    """

    if isinstance(type_definition, element):
        type_definition = type_definition._element__typeDefinition()

    element_map = type_definition._ElementMap
    return tuple(name.localName() for name in element_map.keys())

However, since the _ElementMap is a dict, it yields the keys in random order. I however need the order of the elements, as it is defined in the corresponding XSD. How can I achieve that?