given two dataframes calculate the absolute and relative error of mean values of the columns "NEVs" and "MWhT" grouped by the columns "time" and "Volt" of both dataframes

def absolute_and_relative_error(dataframe_a, dataframe_b):
    absolut_error = (dataframe_a - dataframe_b).abs()
    relative_error = absolut_error.divide(dataframe_a)
    return absolut_error, relative_error

absolute_and_relative_error(df_1, df_2)