DOC Specify the meaning of y=None in fit_transform
@@ -667,9 +667,10 @@ class TransformerMixin:
----------
X : {array-like, sparse matrix, dataframe} of shape \
(n_samples, n_features)
+ Input samples.
y : ndarray of shape (n_samples,), default=None
- Target values.
+ Target values (None for unsupervised transformations).
**fit_params : dict
Additional fit parameters.
