code: def variants(self, case_id, skip=0, count=1000, filters=None):
          
          filters = filters or {}
          logger.debug("Fetching case with case_id: {0}".format(case_id))
          case_obj = self.case(case_id)
          plugin, case_id = self.select_plugin(case_obj)
          self.filters = plugin.filters
  
          gene_lists = (self.gene_list(list_id) for list_id
                        in filters.get('gene_lists', []))
          nested_geneids = (gene_list.gene_ids for gene_list in gene_lists)
          gene_ids = set(itertools.chain.from_iterable(nested_geneids))
  
          if filters.get('gene_ids'):
              filters['gene_ids'].extend(gene_ids)
          else:
              filters['gene_ids'] = gene_ids
          variants = plugin.variants(case_id, skip, count, filters)
          return variants
docs: Fetch variants for a case.