'**SUMMARY**
Compute FREAK Descriptor of given keypoints.
FREAK - Fast Retina Keypoints.
Read more: http://www.ivpe.com/freak.htm
Keypoints can be extracted using following detectors.
- SURF
- SIFT
- BRISK
- ORB
- STAR
- MSER
- FAST
- Dense
**PARAMETERS**
* *flavor* - Detector (see above list of detectors) - string
**RETURNS**
* FeatureSet* - A feature set of KeyPoint Features.
* Descriptor* - FREAK Descriptor
**EXAMPLE**
>>> img = Image("lenna")
>>> fs, des = img.getFREAKDescriptor("ORB")'

def getFREAKDescriptor(self, flavor='SURF'):

    try:
        import cv2
    except ImportError:
        warnings.warn('OpenCV    version    >=    2.4.2    requierd')
        return None
    if cv2.__version__.startswith('$Rev:'):
        warnings.warn('OpenCV    version    >=    2.4.2    requierd')
        return None
    if (int(cv2.__version__.replace('.', '0')) < 20402):
        warnings.warn('OpenCV    version    >=    2.4.2    requierd')
        return None
    flavors = ['SIFT', 'SURF', 'BRISK', 'ORB', 'STAR', 'MSER', 'FAST', 'Dense']
    if (flavor not in flavors):
        warnings.warn('Unkown    Keypoints    detector.    Returning    None.')
        return None
    detector = cv2.FeatureDetector_create(flavor)
    extractor = cv2.DescriptorExtractor_create('FREAK')
    self._mKeyPoints = detector.detect(self.getGrayNumpyCv2())
    (self._mKeyPoints, self._mKPDescriptors) = extractor.compute(self.getGrayNumpyCv2(), self._mKeyPoints)
    fs = FeatureSet()
    for i in range(len(self._mKeyPoints)):
        fs.append(KeyPoint(self, self._mKeyPoints[i], self._mKPDescriptors[i], flavor))
    return (fs, self._mKPDescriptors)
