<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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