docs: def search_variants(self, variant_ids):
          """Make a batch search for variants in the database
          
          Args:
              variant_ids(list(str)): List of variant ids
          
          Returns:
              res(pymngo.Cursor(variant_obj)): The result
          """
          query = {'_id': {'$in': variant_ids}}
          
          return self.db.variant.find(query)