DOC Specify the meaning of dict_init=None in dict_learning_online (sc…

…ikit-learn#23261)

sklearn/decomposition/_dict_learning.py

@@ -808,7 +808,9 @@ def dict_learning_online(
  Whether to also return the code U or just the dictionary `V`.
 
  dict_init : ndarray of shape (n_components, n_features), default=None
- Initial value for the dictionary for warm restart scenarios.
+ Initial values for the dictionary for warm restart scenarios.
+ If `None`, the initial values for the dictionary are created
+ with an SVD decomposition of the data via :func:`~sklearn.utils.randomized_svd`.
 
  callback : callable, default=None
  A callable that gets invoked at the end of each iteration.