There is a Pandas dataframe: year date route operator group_name bus_garage bus_park injury_result incident_type victim_category victim_sex victim_age 0 2015 01.01.2015 1 London General Go-Ahead Garage Not Available Southwark Injuries treated on scene Onboard Injuries Passenger Male Child 1 2015 01.01.2015 4 Metroline Metroline Garage Not Available Islington Injuries treated on scene Onboard Injuries Passenger Male Unknown 2 2015 01.01.2015 5 East London Stagecoach Garage Not Available Havering Taken to Hospital – Reported Serious Injury or... Onboard Injuries Passenger Male Elderly Write a grouped_operators function that groups all values by operator column and sums all dates for each unique operator value

import pandas as pd
data = {'year':[2015,2015,2015],
        'date':['01.01.2015','01.01.2015','01.01.2015'],
        'route':[1,4,5],
        'operator':['London General','Metroline','East London'],
        'group_name':['Go-Ahead','Metroline','Stagecoach'],
        'bus_garage':['Southwark','Islington','Havering'],
        'bus_park':['Garage Not Available','Garage Not Available','Garage Not Available'],
        'injury_result':['Injuries treated on scene','Injuries treated on scene','Taken to Hospital – Reported Serious Injury or...'],
        'incident_type':['Onboard Injuries','Onboard Injuries','Onboard Injuries'],
        'victim_category':['Passenger','Passenger','Passenger'],
        'victim_sex':['Male','Male','Male'],
        'victim_age':['Child','Unknown','Elderly']