Return list of (lineno, indentlevel) pairs.

    One for each stmt and comment line. indentlevel is -1 for comment
    lines, as a signal that tokenize doesn't know what to do about them;
    indeed, they're our headache!

def _reindent_stats(tokens):
    """Return list of (lineno, indentlevel) pairs.

    One for each stmt and comment line. indentlevel is -1 for comment
    lines, as a signal that tokenize doesn't know what to do about them;
    indeed, they're our headache!

    """
    find_stmt = 1  # Next token begins a fresh stmt?
    level = 0  # Current indent level.
    stats = []

    for t in tokens:
        token_type = t[0]
        sline = t[2][0]
        line = t[4]

        if token_type == tokenize.NEWLINE:
            # A program statement, or ENDMARKER, will eventually follow,
            # after some (possibly empty) run of tokens of the form
            #     (NL | COMMENT)* (INDENT | DEDENT+)?
            find_stmt = 1

        elif token_type == tokenize.INDENT:
            find_stmt = 1
            level += 1

        elif token_type == tokenize.DEDENT:
            find_stmt = 1
            level -= 1

        elif token_type == tokenize.COMMENT:
            if find_stmt:
                stats.append((sline, -1))
                # But we're still looking for a new stmt, so leave
                # find_stmt alone.

        elif token_type == tokenize.NL:
            pass

        elif find_stmt:
            # This is the first "real token" following a NEWLINE, so it
            # must be the first token of the next program statement, or an
            # ENDMARKER.
            find_stmt = 0
            if line:   # Not endmarker.
                stats.append((sline, level))

    return stats