class_docstr: Base class for function transformers 
class_docstr_tok: ["Base","class","for","function","transformers"]
code: def transform(self, X, y=None):
      return self.transformer_.transform(X)
  
imports: import warnings
  import pandas
  import numpy
  from scipy import sparse
  from sklearn.base import BaseEstimator, TransformerMixin
  from sklearn.preprocessing import MultiLabelBinarizer, FunctionTransformer, LabelEncoder, normalize
  from sklearn.feature_extraction.text import HashingVectorizer
  from sklearn import feature_selection
label_desc: Use image node_id 2 for calling the _CustomFunctionTransformer obj's underlying member method code with example usage: obj.transform(X, y) and returns: self