def check_repetitive(combination, df_main):
    """Check to avoid repetitive combinations
        
    Parameters
    ----------
    combination: 
        combinations that want to be checked
    
    df_main: pandas.DataFrame
        source dataframe
        
    Returns
    -------
    boolean:
        True: it exists in df_main
        False: it's not
    """
    comparison_df = df_main.merge(combination, indicator=True, how='outer')
    if 'both' in comparison_df._merge.unique():
        return False
    else:
        return True