def post_process_pleonastic_pronoun(system_mentions):
    """ Removes pleonastic it and you.

    These are detected via the following heuristics:
        - it: appears in 'it _ _ that' or 'it _ _ _ that'
        - you: appears in 'you know'

    Args:
        system_mentions (list(Mention): A list of system mentions.

    Returns:
        list(Mention): the filtered list of mentions.
    """
    filtered = []

    for mention in system_mentions:
        if " ".join(mention.attributes["tokens"]).lower() == "it":
            context_two = mention.get_context(2)
            context_three = mention.get_context(3)

            if context_two is not None:
                if context_two[-1] == "that":
                    continue

            if context_three is not None:
                if context_three[-1] == "that":
                    continue

        if " ".join(mention.attributes["tokens"]).lower() == "you":
            if mention.get_context(1) == ["know"]:
                continue

        filtered.append(mention)

    return sorted(filtered)