def col_list(nn):
    """
    Get names for the columns containing Trace value and Signal intensity value
    for a given nearest number of bases, from the dataframe returned by trace_df

    Parameters
    ----------
    nn : int for number of nearest neighbours

    Returns
    -------
    list : list containing column names
    """
    list = []
    for i in range(2 * nn + 1):
        list.append("SI_" + str(i - nn))
    for i in range(2 * nn + 1):
        list.append("TR_" + str(i - nn))
    return list