def get_previous_identifiers(self):
previous_identifiers = None<EOL>stack = self.get_run_as_identifiers_stack()  <EOL>if stack:<EOL><INDENT>if (len(stack) == <NUM_LIT:1>):<EOL><INDENT>previous_identifiers = self.identifiers<EOL><DEDENT>else:<EOL><INDENT>previous_identifiers = stack[<NUM_LIT:1>]<EOL><DEDENT><DEDENT>return previous_identifiers<EOL>
:returns: SimpleIdentifierCollection