read the dataframe "global_dataframe" from csv file "Sum Dat.csv" group by the columns "time" and "Volt" the mean value of the columns "NVEs" and "MWhT", concatenating the values of columns "time" and "Volt"

import pandas as pd
import numpy as np

def load_CSV(file):
    global_dataframe = pd.read_csv(file)
    global_dataframe["time"] = global_dataframe["Date"] + " " + global_dataframe["Time"]
    global_dataframe["time"] = pd.to_datetime(global_dataframe["time"])
    global_dataframe["time"] = global_dataframe["time"].map(lambda x: x.strftime("%Y-%m-%d %H:%M"))
    global_dataframe = global_dataframe.groupby(["time", "Volt"]).agg(
        {"NVEs": np.mean, "MWhT": np.mean})
    global_dataframe = global_dataframe.reset_index()
    return global_dataframe

load_CSV("Sum Dat.csv")