def _get_action(self, action):
<EOL>if action not in self.wsgi_actions:<EOL><INDENT>return None<EOL><DEDENT>if action not in self.wsgi_descriptors:<EOL><INDENT>self.wsgi_descriptors[action] = actions.ActionDescriptor(<EOL>self.wsgi_actions[action],<EOL>self.wsgi_extensions.get(action, []),<EOL>self.wsgi_resp_type)<EOL><DEDENT>return self.wsgi_descriptors[action]<EOL>
Retrieve a descriptor for the named action.  Caches
descriptors for efficiency.