def find_eyes(landmarks):
    """
    Helper method to find all key-value pairs in a dict whose keys reference 'left_eye' and 'right_eye'
    The dictionary should have string keys or it will return a None tuple
    :param landmarks: Dictionary with String keys referencing left and right eyes
    :return: a tuple of lists containing pixel locations of landmarks representing left_eye and right_eye
    """
    left_eye = {}
    right_eye = {}
    for key in landmarks.keys():
        if str(key).startswith("left_eye"):
            left_eye[key] = landmarks[key]
        elif key.startswith("right_eye"):
            right_eye[key] = landmarks[key]
    return left_eye, right_eye