import pandas as pd
from sklearn.compose import ColumnTransformer
from sklearn.impute import SimpleImputer
from sklearn.pipeline import Pipeline
from sklearn.preprocessing import OneHotEncoder, StandardScaler


train = pd.DataFrame(
    {
        "age": [22, 35, None, 48],
        "fare": [120, 340, 210, None],
        "city": ["London", "Paris", "London", "Berlin"],
        "plan": ["basic", "premium", "premium", "basic"],
    }
)
holdout = pd.DataFrame(
    {
        "age": [31, 50],
        "fare": [180, None],
        "city": ["Rome", "London"],
        "plan": ["premium", "basic"],
    }
)
numeric_features = ["age", "fare"]
categorical_features = ["city", "plan"]