diff --git a/swh/indexer/metadata_dictionary/base.py b/swh/indexer/metadata_dictionary/base.py
--- a/swh/indexer/metadata_dictionary/base.py
+++ b/swh/indexer/metadata_dictionary/base.py
@@ -159,9 +159,7 @@
 
         return simple_terms | complex_terms
 
-    def _translate_dict(
-        self, content_dict: Dict, *, normalize: bool = True
-    ) -> Dict[str, str]:
+    def _translate_dict(self, content_dict: Dict) -> Dict[str, str]:
         """
         Translates content  by parsing content from a dict object
         and translating with the appropriate mapping
@@ -209,10 +207,15 @@
                 else:
                     translated_metadata[codemeta_key] = v
 
-        if normalize:
-            return self.normalize_translation(translated_metadata)
-        else:
-            return translated_metadata
+        self.extra_translation(translated_metadata, content_dict)
+
+        return self.normalize_translation(translated_metadata)
+
+    def extra_translation(self, translated_metadata: Dict[str, Any], d: Dict[str, Any]):
+        """Called at the end of the translation process, and may add arbitrary keys
+        to ``translated_metadata`` based on the input dictionary (passed as ``d``).
+        """
+        pass
 
 
 class JsonMapping(DictMapping):
diff --git a/swh/indexer/metadata_dictionary/maven.py b/swh/indexer/metadata_dictionary/maven.py
--- a/swh/indexer/metadata_dictionary/maven.py
+++ b/swh/indexer/metadata_dictionary/maven.py
@@ -41,13 +41,15 @@
         if not isinstance(d, dict):
             self.log.warning("Skipping ill-formed XML content: %s", content)
             return None
-        metadata = self._translate_dict(d, normalize=False)
-        metadata[SCHEMA.codeRepository] = self.parse_repositories(d)
-        metadata[SCHEMA.license] = self.parse_licenses(d)
-        return self.normalize_translation(metadata)
+        return self._translate_dict(d)
 
     _default_repository = {"url": "https://repo.maven.apache.org/maven2/"}
 
+    def extra_translation(self, translated_metadata, d):
+        repositories = self.parse_repositories(d)
+        if repositories:
+            translated_metadata[SCHEMA.codeRepository] = repositories
+
     def parse_repositories(self, d):
         """https://maven.apache.org/pom.html#Repositories
 
@@ -102,7 +104,12 @@
         if isinstance(id_, str):
             return {"@id": id_}
 
-    def parse_licenses(self, d):
+    def translate_licenses(self, translated_metadata, d):
+        licenses = self.parse_licenses(d)
+        if licenses:
+            translated_metadata[SCHEMA.license] = licenses
+
+    def parse_licenses(self, licenses):
         """https://maven.apache.org/pom.html#Licenses
 
         >>> import xmltodict
@@ -124,7 +131,7 @@
                 }
             }
         }
-        >>> MavenMapping().parse_licenses(d)
+        >>> MavenMapping().parse_licenses(d["licenses"])
         [{'@id': 'https://www.apache.org/licenses/LICENSE-2.0.txt'}]
 
         or, if there are more than one license:
@@ -143,12 +150,11 @@
         ...   </license>
         ... </licenses>
         ... ''')
-        >>> pprint(MavenMapping().parse_licenses(d))
+        >>> pprint(MavenMapping().parse_licenses(d["licenses"]))
         [{'@id': 'https://www.apache.org/licenses/LICENSE-2.0.txt'},
          {'@id': 'https://opensource.org/licenses/MIT'}]
         """
 
-        licenses = d.get("licenses")
         if not isinstance(licenses, dict):
             return
         licenses = licenses.get("license")
diff --git a/swh/indexer/metadata_dictionary/python.py b/swh/indexer/metadata_dictionary/python.py
--- a/swh/indexer/metadata_dictionary/python.py
+++ b/swh/indexer/metadata_dictionary/python.py
@@ -52,12 +52,13 @@
             key = _normalize_pkginfo_key(key)
             if value != "UNKNOWN":
                 d.setdefault(key, []).append(value)
-        metadata = self._translate_dict(d, normalize=False)
+        return self._translate_dict(d)
 
-        author_name = metadata.pop(SCHEMA.author, None)
-        author_email = metadata.pop(SCHEMA.email, None)
+    def extra_translation(self, translated_metadata, d):
+        author_name = translated_metadata.pop(SCHEMA.author, None)
+        author_email = translated_metadata.pop(SCHEMA.email, None)
         if author_name or author_email:
-            metadata[SCHEMA.author] = {
+            translated_metadata[SCHEMA.author] = {
                 "@list": [
                     {
                         "@type": SCHEMA.Person,
@@ -66,7 +67,6 @@
                     }
                 ]
             }
-        return self.normalize_translation(metadata)
 
     def normalize_home_page(self, urls):
         return [{"@id": url} for url in urls]