def generate_colnames(df):
    """Generates column names for an input dataframe.

    Arguments:
        df {dataframe} -- [dataframe for which column names are generated]

    Returns:
        [list] -- [list of generated colum names]
    """
    colnames = ["CHR", "START", "END"]
    for i in range(df.columns.str.contains("usercol").sum()-3):
        colnames.append("label_{}".format(i+1))
    colnames.append("gc")
    colnames.append("num_N")
    return colnames