docs: def _parse_lookup_string(self, lookup_chain):
          """Convert a lookup string to a (lookup_chain, comparator) tuple."""
          lookup_chain = lookup_chain.split('__')
          comparator = self.default_comparator
  
          # Only look for a lookup method if the lookup chain is larger than 1
          if len(lookup_chain) <= 1:
              return lookup_chain, comparator
  
          # Get the correct lookup_method if the last value in the lookup
          # chain is a lookup method specifier
          if lookup_chain[-1] in self.comparators:
              comparator = self.comparators.get(lookup_chain.pop(-1))
  
          return lookup_chain, comparator