_, _ := self.call(http.Method.put, 'profile/$escaped_user_id/displayname', name_data.str()) ?

		user_part := if user_id.len > 0 { '?user_id=$user_id' } else { '' }
		_, _ := self.call(http.Method.put, 'profile/$escaped_user_id/displayname?$user_part',
			name_data.str()) ?