code: def fit(self, X, y=None):
      return self
  
imports: import dask.dataframe
  import numpy
  import packaging.version
  import pandas
  import pytest
  import sklearn.compose
  import sklearn.pipeline
  import sklearn.preprocessing
  from sklearn.base import BaseEstimator, clone
  import dask_ml.compose
  import dask_ml.preprocessing
  from dask_ml._compat import SK_VERSION
label_desc: Use image node_id 2 for calling the SumTransformer obj's underlying member method code with example usage: obj.fit(X, y) and returns: self