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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 init(req, model):
 # pylint: disable=unused-argument """ Determine the sparse fields to limit the response to Return a dict where the key is the resource type (rtype) & the value is an array of string fields names to whitelist against. :return: dict """


    params = {}

    for key, val in req.params.items():
        try:
            rtype, fields = _parse_param(key, val)
            params[rtype] = fields
        except TypeError:
            continue

    if params:
        _validate_req(req)
        for rtype, fields in params.items():
            _validate_param(rtype, fields)
    return params