def normalize_mark_list(mark_list):
extracted = [<EOL>getattr(mark, "<STR_LIT>", mark) for mark in mark_list<EOL>]  <EOL>for mark in extracted:<EOL><INDENT>if not isinstance(mark, Mark):<EOL><INDENT>raise TypeError("<STR_LIT>".format(mark))<EOL><DEDENT><DEDENT>return [x for x in extracted if isinstance(x, Mark)]<EOL>
normalizes marker decorating helpers to mark objects

:type mark_list: List[Union[Mark, Markdecorator]]
:rtype: List[Mark]