Fixes pandas deprecation for indexing

        if index is None:

            keypoints = self.keypoints[['x', 'y']]

        else:

            keypoints = self.keypoints.loc[index][['x', 'y']]

            keypoints = self.keypoints.loc[self.keypoints.index.intersection(index)][['x', 'y']]

        if homogeneous:

            keypoints['homogeneous'] = 1

        new_keypoints, new_descriptors = Node._extract_features(array, *args, **kwargs)

        count = len(self.keypoints)

        if camera:

            # Project the sift keypoints to the ground

            def func(row, args):

                camera = args[0]

                gnd = getattr(camera, 'imageToGround')(row[1], row[0], 0)

                return gnd

            feats = new_keypoints[['x', 'y']].values

            gnd = np.apply_along_axis(func, 1, feats, args=(camera, ))

            gnd = pd.DataFrame(gnd, columns=['xm', 'ym', 'zm'], index=keypoints.index)

            keypoints = pd.concat([keypoints, gnd], axis=1)

        # If this is a tile, push the keypoints to the correct start xy

        if xystart:

            new_keypoints['x'] += xystart[0]

            new_keypoints['y'] += xystart[1]

        concat_kps = pd.concat((self.keypoints, new_keypoints))

        descriptor_mask = concat_kps.duplicated()

        descriptor_mask = descriptor_mask[count:]        

        # Removed duplicated and re-index the merged keypoints

        concat_kps.drop_duplicates(inplace=True)

        descriptor_mask = concat_kps.duplicated(keep='last')

        concat_kps.reset_index(inplace=True, drop=True)

        concat_kps.drop_duplicates(inplace=True)

        #descriptor_mask = descriptor_mask[count:]        

        # Removed duplicated and re-index the merged keypoints

        if self.descriptors is not None:

            concat = np.concatenate((self.descriptors, new_descriptors[~descriptor_mask]))

            self.descriptors = concat

        else:

            concat = np.concatenate((self.descriptors, new_descriptors))

            new_descriptors = concat[concat_kps.index]

        self.descriptors = new_descriptors

        self.keypoints = concat_kps

        lkps = len(self.keypoints)

        print(lkps, len(self.descriptors))

        assert lkps == len(self.descriptors)

        if lkps > 0:

        if len(self.keypoints) > 0:

            return True

    def project_keypoints(self):   

        if self.camera is None:

            # Without a camera, it is not possible to project

            warnings.warn('Unable to project points, no camera available.')

            return False

        # Project the sift keypoints to the ground

        def func(row, args):

            camera = args[0]

            gnd = getattr(camera, 'imageToGround')(row[1], row[0], 0)

            return gnd

        feats = self.keypoints[['x', 'y']].values

        gnd = np.apply_along_axis(func, 1, feats, args=(self.camera, ))

        gnd = pd.DataFrame(gnd, columns=['xm', 'ym', 'zm'], index=self.keypoints.index)

        self.keypoints = pd.concat([self.keypoints, gnd], axis=1)

        return True

    def load_features(self, in_path, format='npy', **kwargs):

        """

        Load keypoints and descriptors for the given image