Chapter 2: TypeError: 'SimpleImputer' object is not callable

from sklearn.pipeline import Pipeline
from sklearn.preprocessing import StandardScaler
num_pipeline = Pipeline([
('SimpleImputer', SimpleImputer(strategy="median")),
('attribs_adder', CombinedAttributesAdder()),
('std_scaler', StandardScaler()),
])
housing_num_tr = num_pipeline.fit_transform(housing_num)

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TypeError Traceback (most recent call last)
in
2 from sklearn.preprocessing import StandardScaler
3 num_pipeline = Pipeline([
----> 4 ('SimpleImputer', SimpleImputer(strategy="median")),
5 ('attribs_adder', CombinedAttributesAdder()),
6 ('std_scaler', StandardScaler()),

TypeError: 'SimpleImputer' object is not callable

Any help please?