def url_to_prefix(self, id):
ret = re.search('<STR_LIT>', id)<EOL>if ret:<EOL><INDENT>return self.urls[ret.group(<NUM_LIT:1>)] + '<STR_LIT::>' + ret.group(<NUM_LIT:2>)<EOL><DEDENT>else:<EOL><INDENT>return id<EOL><DEDENT>
url_to_prefix

        High-level api: Convert an identifier from `{namespace}tagname` notation
        to `prefix:tagname` notation. If the identifier does not have a
        namespace, it is assumed that the whole identifier is a tag name.

        Parameters
        ----------

        id : `str`
            Identifier in `{namespace}tagname` notation.

        Returns
        -------

        str
            Identifier in `prefix:tagname` notation.