def _iterate_subsequences(self, tokens):
for start_idx in xrange(len(tokens)):<EOL><INDENT>for end_idx in xrange(start_idx + <NUM_LIT:1>, len(tokens) + <NUM_LIT:1>):<EOL><INDENT>yield '<STR_LIT:U+0020>'.join(tokens[start_idx:end_idx]), start_idx<EOL><DEDENT><DEDENT>
Using regex invokes this function, which significantly impacts performance of adapt. it is an N! operation.

Args:
    tokens(list): list of tokens for Yield results.

Yields:
    str: ?