def get_identifier(self):
if '<STR_LIT>' in self.options:<EOL><INDENT>return self.options['<STR_LIT>']<EOL><DEDENT>title_nodes = self.state.document.traverse(nodes.title)<EOL>if not title_nodes:<EOL><INDENT>raise DisqusError('<STR_LIT>')<EOL><DEDENT>return title_nodes[<NUM_LIT:0>].astext()<EOL>
Validate and returns disqus_identifier option value.

        :returns: disqus_identifier config value.
        :rtype: str