# import necessary libraries
import pandas as pd
import numpy as np

# create sample series
fruits = pd.Series(['apple', 'banana', 'mango', 'apple',
                      'mango', 'apple', 'apple', 'banana'])
values = pd.Series([1, 2, 3, 4, 5, 6, 7, 8])

# create a dataframe
df = pd.DataFrame({'fruits': fruits, 'values': values})

# calculate mean of grouped values using pd.pivot_table()
grouped_mean = pd.pivot_table(df, values = 'values',
                              index = 'fruits', 
                              aggfunc = np.mean)

# print the results
print(grouped_mean)