def pp_Age(df):
    """
    imputes missing values of age through a groupby([Pclass,Title,isFemale])
    returns df with new column named Age_nonull appended to it
    """
    transformed_Age = df.groupby(["Title", 'Pclass', "Sex"])['Age'].transform(lambda x: x.fillna(x.median()))
    df['Age_nonull'] = transformed_Age
    return df