def get_cited_paperids(conn, paperid,
                       original_paper_col='paperid', cite_col='refpaperid',
                       citations_table='semantic.citations'):
    """
    Get all of the paperids cited by one paperid. If cited papers exist, returns
    a list of those paperids, otherwise returns None.

    Parameters
    ==========
    conn : SQLConn connection
    paperid : str
    original_paper_col : str
    cite_col : str
    citations_table : str

    Returns
    =======
    cited_paperids : list
    """

    query = f"select {cite_col} from {citations_table} where {original_paper_col}='{paperid}';"
    cited_paperids = conn.query(query)

    if cited_paperids.shape[0] > 0:
        return cited_paperids[cite_col].to_list()
    else:
        return None