refactor(resources): use walrus in add_resource_template duplicate check

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: mplemay

src/mcp/server/mcpserver/resources/resource_manager.py

@@ -76,8 +76,7 @@ def add_resource_template(self, template: ResourceTemplate) -> ResourceTemplate:
                 "resource_name": template.name,
             },
         )
-        existing = self._templates.get(template.uri_template)
-        if existing:
+        if existing := self._templates.get(template.uri_template):
             if self.warn_on_duplicate_resources:
                 logger.warning(f"Resource template already exists: {template.uri_template}")
             return existing