fixing

Author: Avi-Robusta

src/robusta/core/sinks/slack/preview/slack_sink_preview_params.py

@@ -20,15 +20,15 @@ def get_effective_template_name(self) -> str:
         Otherwise, use 'legacy.j2' if template_style is legacy, else 'header.j2'.
         """
         if self.slack_custom_templates and len(self.slack_custom_templates) == 1:
-            return self.slack_custom_templates.keys()[0]
+            return next(iter(self.slack_custom_templates))
         return "header.j2"
 
     def get_custom_template(self) -> Optional[str]:
         """
         Returns the custom template string for the effective template name, if it exists.
         """
         if self.slack_custom_templates and len(self.slack_custom_templates) == 1:
-            return self.slack_custom_templates.values()[0]
+            return next(iter(self.slack_custom_templates))
         return None