code: func (api *API) Filter(zoneID, filterID string) (Filter, error) {
  	uri := fmt.Sprintf("/zones/%s/filters/%s", zoneID, filterID)
  
  	res, err := api.makeRequest("GET", uri, nil)
  	if err != nil {
  		return Filter{}, errors.Wrap(err, errMakeRequestError)
  	}
  
  	var filterResponse FilterDetailResponse
  	err = json.Unmarshal(res, &filterResponse)
  	if err != nil {
  		return Filter{}, errors.Wrap(err, errUnmarshalError)
  	}
  
  	return filterResponse.Result, nil
  }
docs: // Filter returns a single filter in a zone based on the filter ID.
  //
  // API reference: https://developers.cloudflare.com/firewall/api/cf-filters/get/#get-by-filter-id