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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _as_document(self, identifier):
 """ Converts given identifier to the document indexed by FTS backend. Args: identifier (dict):
 identifier to convert. Dict contains at least 'identifier', 'type' and 'name' keys. Returns: dict with structure matches to BaseIdentifierIndex._schema. """

        return {
            'identifier': u('{}').format(identifier['identifier']),
            'type': u('{}').format(identifier['type']),
            'name': u('{}').format(identifier['name'])
        }