<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def convert_type_list_elements( list_object = None, element_type = str ):
 """ Recursively convert all elements and all elements of all sublists of a list to a specified type and return the new list. """

    if element_type is str:
        return [str(element) if not isinstance(element, list) else convert_type_list_elements(
            list_object  = element,
            element_type = str
        ) for element in list_object]