fix docstring typo and attribute

Author: kosack

docs/changes/2928.feature.rst

@@ -39,4 +39,4 @@ The functionality of `~ctapipe.io.DL2EventLoader` can be mimicked with the follo
 This also introduces a helper function `~ctapipe.coordinates.altaz_to_nominal`
 to convert columns of alt/az coordinates to FOV coordinates in the
 `~ctapipe.coordinates.NominalFrame`, which works with the
-`~ctapipe.io.FeatureGenerator`.
+`~ctapipe.core.FeatureGenerator`.

src/ctapipe/io/event_preprocessor.py

@@ -34,11 +34,11 @@ class EventPreprocessor(Component):
     `~ctapipe.core.FeatureGenerator` and set the ``features`` property of this
     class with the columns you to retain in the output table.
 
-    In the `~ctapipe.core.FeatureGenerator`` used internally, you have access to several
-    additional functions useful for DL2 processing:
+    In the `~ctapipe.core.FeatureGenerator` used internally, you have access to
+    several additional functions useful for DL2 processing:
 
-      - `~astropy.coordinates.angular_separation`
-      - `~ctapipe.coordinates.altaz_to_nominal`
+    - `~astropy.coordinates.angular_separation`
+    - `~ctapipe.coordinates.altaz_to_nominal`
     """
 
     energy_reconstructor = traits.Unicode(
@@ -177,7 +177,7 @@ def _get_predefined_quality_criteria(self) -> list[tuple]:
             raise NotImplementedError(f"unsupported feature_set: {self.feature_set}")
 
     @default("features")
-    def default_features(self):
+    def _features(self):
         """Set the columns to output, for a given FeatureSet."""
         if self.feature_set == PreprocessorFeatureSet.dl2_irf:
             return [