def drop_null(dataframe, inplace=True):
    """Drop null tickets

    Parameters
    ----------
    dataframe : pandas.DataFrame
    inplace : bool

    Returns
    -------
    If `inplace` is False, returns the input dataframe with the null citations removed.
    """
    if not inplace:
        dataframe = dataframe.copy()

    null_indices = dataframe.ticket_number.isnull()
    dataframe.drop(index=dataframe.index[null_indices], inplace=True)
    if not inplace:
        return dataframe