def extract(self, lon, l, b, r, **kwargs):
        """
        Extract a feature vector from a postage stamp description

        Paramters
        ---------
        lon : int
            The longitude of the field to use
        l : float
            Bubble center longitude, degrees
        b : float
            Bubble center latitude, degrees
        r : float
            Bubble radius, degrees

        Returns
        -------
        A feature vector. The contents of the feature vector
        are configured by subclasses
        """
        kwargs.setdefault('limits', [1, 97])
        kwargs.setdefault('shp', self.shp)

        rgb = get_field(lon).extract_stamp(l, b, r, **kwargs)

        if rgb is None:
            raise ValueError("Field is out of bounds")
        elif 0.1 > (rgb[:, :, 1] == 0).mean():
            raise ValueError("Field has no green channel")

        rgb = self._preprocess_rgb(rgb)
        return self._extract_rgb(rgb)
dataset/ETHPy150Open ChrisBeaumont/brut/bubbly/extractors.py/Extractor.extract/swapped operands of `>`