docs: def reverse_lookup(self, state, path):
          """
          Returns a chrome URL for a given path, given the current package depth
          in an error bundle.
  
          State may either be an error bundle or the actual package stack.
          """
  
          # Make sure the path starts with a forward slash.
          if not path.startswith('/'):
              path = '/%s' % path
  
          # If the state is an error bundle, extract the package stack.
          if not isinstance(state, list):
              state = state.package_stack
  
          content_paths = self.get_triples(subject='content')
          for content_path in content_paths:
              chrome_name = content_path['predicate']
              if not content_path['object']:
                  continue
              path_location = content_path['object'].split()[0]
  
              if path_location.startswith('jar:'):
                  if not state:
                      continue
  
                  # Parse out the JAR and it's location within the chrome.
                  split_jar_url = path_location[4:].split('!', 2)
                  # Ignore invalid/unsupported JAR URLs.
                  if len(split_jar_url) != 2:
                      continue
  
                  # Unpack the JAR URL.
                  jar_path, package_path = split_jar_url
  
                  if jar_path != state[0]:
                      continue
  
                  return 'chrome://%s' % self._url_chunk_join(chrome_name,
                                                              package_path,
                                                              path)
              else:
                  if state:
                      continue
  
                  path_location = '/%s/' % path_location.strip('/')
                  rel_path = os.path.relpath(path, path_location)
  
                  if rel_path.startswith('../') or rel_path == '..':
                      continue
  
                  return 'chrome://%s' % self._url_chunk_join(chrome_name,
                                                              rel_path)
  
          return None