def group_aggregation(df, group_var, agg_var):
    """
        We need to group the Auto MPG Dataset on the basis of a column. 
        Then we have to calculate the mean of the grouped data according to another column
        
        parameters
            df: A dataframe containing the dataset in the form of a matrix.
            group_var: A variable that will group the data
            agg_var: A variable to aggregate or describe the grouped data with statistics
            
        returns
            dataframe
    """

    # Grouping the data and taking mean
    grouped_df = df.groupby([group_var])[agg_var].mean()
    return grouped_df