Imputer in Python

#Check for null values in the data-set. If any, impute those missing values using simple imputer. (Hint: Use 'median' to impute)find out the mean of 'enginesize' after imputing
import pandas as pd
import numpy as np
# Importing the SimpleImputer class 
from sklearn.impute import SimpleImputer
imputer = SimpleImputer(missing_values=np.NaN, strategy='median')
df.enginesize = imputer.fit_transform(df['enginesize'].values.reshape(-1,1))[:,0]
df['enginesize'].mean()