Fix weight doc generation (#5874)

docs/source/conf.py

@@ -326,7 +326,15 @@ def inject_weight_metadata(app, what, name, obj, options, lines):
                 lines += [f"This weight is also available as ``{obj.__name__}.DEFAULT``.", ""]
 
             table = []
-            for k, v in field.meta.items():
+
+            # the `meta` dict contains another embedded `metrics` dict. To
+            # simplify the table generation below, we create the
+            # `meta_with_metrics` dict, where the metrics dict has been "flattened"
+            meta = field.meta
+            metrics = meta.pop("metrics", {})
+            meta_with_metrics = dict(meta, **metrics)
+
+            for k, v in meta_with_metrics.items():
                 if k == "categories":
                     continue
                 elif k == "recipe":