DOC Corrects links to doc of ClassifierChain and RegressorChain (scikit-learn#10288)

Author: thechargedneutron

doc/modules/multiclass.rst

@@ -397,7 +397,7 @@ Below is an example of multioutput classification:
            [0, 0, 2],
            [2, 0, 0]])
 
-.. classifierchain:
+.. _classifierchain:
 
 Classifier Chain
 ================
@@ -428,7 +428,7 @@ averaged together.
     Jesse Read, Bernhard Pfahringer, Geoff Holmes, Eibe Frank,
         "Classifier Chains for Multi-label Classification", 2009.
 
-.. regressorchain:
+.. _regressorchain:
 
 Regressor Chain
 ================

sklearn/multioutput.py

@@ -536,6 +536,12 @@ class labels for each estimator in the chain.
     order_ : list
         The order of labels in the classifier chain.
 
+    See also
+    --------
+    RegressorChain: Equivalent for regression
+    MultioutputClassifier: Classifies each output independently rather than
+        chaining.
+
     References
     ----------
     Jesse Read, Bernhard Pfahringer, Geoff Holmes, Eibe Frank, "Classifier
@@ -681,6 +687,12 @@ class RegressorChain(_BaseChain, RegressorMixin, MetaEstimatorMixin):
     order_ : list
         The order of labels in the classifier chain.
 
+    See also
+    --------
+    ClassifierChain: Equivalent for classification
+    MultioutputRegressor: Learns each output independently rather than
+        chaining.
+
     """
     def fit(self, X, Y):
         """Fit the model to data matrix X and targets Y.