text: from sklearn.base import TransformerMixin
  
  
  class DenseTransformer(TransformerMixin):
  
      def transform(self, X, y=None, **fit_params):
          return X.todense()
  
      def fit_transform(self, X, y=None, **fit_params):
          self.fit(X, y, **fit_params)
          return self.transform(X)
  
      def fit(self, X, y=None, **fit_params):
          return self