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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 fetch(cls, id, api_key=None, endpoint=None, add_headers=None, **kwargs):
 """ Fetch a single entity from the API endpoint. Used when you know the exact ID that must be queried. """

        if endpoint is None:
            endpoint = cls.get_endpoint()

        inst = cls(api_key=api_key)
        parse_key = cls.sanitize_ep(endpoint).split("/")[-1]
        endpoint = '/'.join((endpoint, id))
        data = cls._parse(inst.request('GET',
                                       endpoint=endpoint,
                                       add_headers=add_headers,
                                       query_params=kwargs),
                          key=parse_key)
        inst._set(data)
        return inst