import re


def remove_tags(sent: str) -> str:
    """
    Replace every tag with "_".

    Parameters
    ----------
    sent: str
        Input string on CoNLL-U format.

    Returns
    -------
    str:
        Processed string.
    """
    return re.sub(
        r"(^\d+(?:\-\d+)?\t*(?:[^\t]*)\t(?:[^\t]*)\t)(\w+)",
        r"\1_",
        sent,
        flags=re.MULTILINE,
    )