<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def get_ordered_children(self):
 """ Return the list of children ordered according to the element structure :return: a list of :class:`Element <hl7apy.core.Element>` """

        ordered_keys = self.element.ordered_children if self.element.ordered_children is not None else []
        children = [self.indexes.get(k, None) for k in ordered_keys]
        return children