Determine if there are elements not in the children
    that need to be included as blank elements in the form.

def add_missing_children(required_children, element_children):
    """Determine if there are elements not in the children
    that need to be included as blank elements in the form.
    """
    element_tags = [element.tag for element in element_children]
    # Loop through the elements that should be in the form.
    for contained_element in required_children:
        # If the element doesn't exist in the form,
        # add the element to the children.
        if contained_element not in element_tags:
            try:
                added_child = PYUNTL_DISPATCH[contained_element](content='')
            except:
                added_child = PYUNTL_DISPATCH[contained_element]()
            element_children.append(added_child)
    return element_children