Address more PR feedback

doc/reference.rst

@@ -252,17 +252,6 @@ Utilities
 
     econml.utilities
 
-Solutions
----------
-
-Causal Feature Importance
-^^^^^^^^^^^^^^^^^^^^^^^^^
-
-.. autosummary::
-    :toctree: _autosummary
-
-    econml.solutions.causal_analysis
-
 Private Module Reference
 ========================
 

econml/solutions/causal_analysis/_causal_analysis.py

@@ -319,6 +319,12 @@ def fit(self, X, y, warm_start=False):
         if heterogeneity_inds == [] or isinstance(heterogeneity_inds[0], (int, str, bool)):
             heterogeneity_inds = [heterogeneity_inds for _ in train_inds]
 
+        # heterogeneity inds should be a 2D list of length same as train_inds
+        elif heterogeneity_inds is not None and len(heterogeneity_inds) != len(train_inds):
+            raise ValueError("Heterogeneity indexes should have the same number of entries, but here "
+                             f" there were {len(heterogeneity_inds)} heterogeneity entries but "
+                             f" {len(train_inds)} feature indices.")
+
         # replace None elements of heterogeneity_inds and ensure indices are numeric
         heterogeneity_inds = {ind: list(range(X.shape[1])) if hinds is None else _get_column_indices(X, hinds)
                               for ind, hinds in zip(train_inds, heterogeneity_inds)}