tuf.api: simplify metadata.Targets.signable()

Signed-off-by: Teodora Sechkova <[email protected]>

Author: sechkova

tuf/api/metadata.py

@@ -185,24 +185,13 @@ def read_from_json(self, filename: str) -> None:
     def signable(self):
         # TODO: probably want to generalise this, a @property.getter in Metadata?
         expires = self.expiration.replace(tzinfo=None).isoformat()+'Z'
-        if self.delegations is not None:
-            return tuf.formats.build_dict_conforming_to_schema(
-                tuf.formats.TARGETS_SCHEMA,
-                version=self.version,
-                expires=expires,
-                targets=self.targets,
-                delegations=self.delegations)
-        else:
-            return tuf.formats.build_dict_conforming_to_schema(
-                tuf.formats.TARGETS_SCHEMA,
-                version=self.version,
-                expires=expires,
-                targets=self.targets)
-        # TODO: As an alternative to the odd if/else above where we decide whether or
-        #       not to include the delegations argument based on whether or not it is
-        #       None, consider instead adding a check in
-        #       build_dict_conforming_to_schema that skips a keyword if that keyword
-        #       is optional in the schema and the value passed in is set to None....
+        return tuf.formats.build_dict_conforming_to_schema(
+            tuf.formats.TARGETS_SCHEMA,
+            version=self.version,
+            expires=expires,
+            targets=self.targets,
+            delegations=self.delegations)
+
 
     # Add or update metadata about the target.
     # TODO: how to handle writing consistent targets?