code: def check_existing_vr_tag(self):
          
          primary_images = get_primary_images(self.workflow)
  
          if not primary_images:
              return
  
          vr_image = None
          for image in primary_images:
              if '-' in image.tag:
                  vr_image = image
                  break
          if not vr_image:
              return
  
          should_fail = False
          for registry_name, registry in self.registries.items():
              pullspec = vr_image.copy()
              pullspec.registry = registry_name
              insecure = registry.get('insecure', False)
              secret = registry.get('secret', None)
  
              manifest_list = get_manifest_list(pullspec, registry_name, insecure, secret)
  
              if manifest_list:
                  self.log.error("Primary tag already exists in registry: %s", pullspec)
                  should_fail = True
  
          if should_fail:
              raise RuntimeError("Primary tag already exists in registry")
docs: Checks if version-release tag (primary not floating tag) exists already,
          and fails plugin if it does.