How to use the regions.core.attributes.QuantityLength function in regions

width : `~astropy.units.Quantity`
        The width of the ellipse (before rotation) as an angle
    height : `~astropy.units.Quantity`
        The height of the ellipse (before rotation) as an angle
    angle : `~astropy.units.Quantity`, optional
        The rotation angle of the ellipse, measured anti-clockwise. If set to
        zero (the default), the width axis is lined up with the longitude axis
        of the celestial coordinates.
    meta : `~regions.RegionMeta` object, optional
        A dictionary which stores the meta attributes of this region.
    visual : `~regions.RegionVisual` object, optional
        A dictionary which stores the visual meta attributes of this region.
    """
    _params = ('center', 'width', 'height', 'angle')
    center = ScalarSky('center')
    width = QuantityLength('width')
    height = QuantityLength('height')
    angle = QuantityLength('angle')

    def __init__(self, center, width, height, angle=0. * u.deg, meta=None, visual=None):
        self.center = center
        self.width = width
        self.height = height
        self.angle = angle
        self.meta = meta or RegionMeta()
        self.visual = visual or RegionVisual()

    def to_pixel(self, wcs):
        center, scale, north_angle = skycoord_to_pixel_scale_angle(self.center, wcs)
        # FIXME: The following line is needed to get a scalar PixCoord
        center = PixCoord(float(center.x), float(center.y))
        height = self.height.to('deg').value * scale

e = Ellipse2D(amplitude=100., x_0=x0, y_0=y0, a=a, b=b, theta=theta.radian)
        y, x = np.mgrid[0:20, 0:30]
        fig, ax = plt.subplots(1, 1)
        ax.imshow(e(x, y), origin='lower', interpolation='none', cmap='Greys_r')

        center = PixCoord(x=x0, y=y0)
        reg = EllipsePixelRegion(center=center, width=2*a, height=2*b, angle=theta)
        patch = reg.as_artist(facecolor='none', edgecolor='red', lw=2)
        ax.add_patch(patch)

    """
    _params = ('center', 'width', 'height', 'angle')
    center = ScalarPix('center')
    width = ScalarLength('width')
    height = ScalarLength('height')
    angle = QuantityLength('angle')

    def __init__(self, center, width, height, angle=0. * u.deg, meta=None,
                 visual=None):
        self.center = center
        self.width = width
        self.height = height
        self.angle = angle
        self.meta = meta or RegionMeta()
        self.visual = visual or RegionVisual()

    @property
    def area(self):
        """Region area (float)"""
        return math.pi / 4 * self.width * self.height

    def contains(self, pixcoord):

Parameters
    ----------
    center : `~astropy.coordinates.SkyCoord`
        The position of the center of the annulus.
    inner_radius : `~astropy.units.Quantity`
        The inner radius of the annulus in angular units
    outer_radius : `~astropy.units.Quantity`
        The outer radius of the annulus in angular units
    meta : `~regions.RegionMeta` object, optional
        A dictionary which stores the meta attributes of this region.
    visual : `~regions.RegionVisual` object, optional
        A dictionary which stores the visual meta attributes of this region.
    """
    _params = ("center", "inner_radius", "outer_radius")
    center = ScalarSky("center")
    inner_radius = QuantityLength("inner_radius")
    outer_radius = QuantityLength("outer_radius")

    def __init__(self, center, inner_radius, outer_radius, meta=None, visual=None):
        self.center = center
        self.inner_radius = inner_radius
        self.outer_radius = outer_radius
        self.meta = meta or RegionMeta()
        self.visual = visual or RegionVisual()

    def to_pixel(self, wcs):
        center, scale, _ = skycoord_to_pixel_scale_angle(self.center, wcs)
        # FIXME: The following line is needed to get a scalar PixCoord
        center = PixCoord(float(center.x), float(center.y))
        inner_radius = self.inner_radius.to("deg").value * scale
        outer_radius = self.outer_radius.to("deg").value * scale
        return CircleAnnulusPixelRegion(

A circle defined using sky coordinates.

    Parameters
    ----------
    center : `~astropy.coordinates.SkyCoord`
        Center position
    radius : `~astropy.units.Quantity`
        Radius in angular units
    meta : `~regions.RegionMeta` object, optional
        A dictionary which stores the meta attributes of this region.
    visual : `~regions.RegionVisual` object, optional
        A dictionary which stores the visual meta attributes of this region.
    """
    _params = ('center', 'radius')
    center = ScalarSky('center')
    radius = QuantityLength("radius")

    def __init__(self, center, radius, meta=None, visual=None):
        self.center = center
        self.radius = radius
        self.meta = meta or RegionMeta()
        self.visual = visual or RegionVisual()

    def to_pixel(self, wcs):
        center, scale, _ = skycoord_to_pixel_scale_angle(self.center, wcs)
        radius = self.radius.to('deg').value * scale
        return CirclePixelRegion(center, radius, self.meta, self.visual)

class AsymmetricAnnulusSkyRegion(SkyRegion):
    """Helper class for asymmetric annuli sky regions.

    Used for ellipse and rectangle annuli below.
    """
    _params = (
        "center",
        "inner_width",
        "inner_height",
        "outer_width",
        "outer_height",
        "angle",
    )
    center = ScalarSky("center")
    inner_width = QuantityLength("inner_width")
    outer_width = QuantityLength("outer_width")
    inner_height = QuantityLength("inner_height")
    outer_height = QuantityLength("outer_height")
    angle = QuantityLength("angle")

    def __init__(
            self,
            center,
            inner_width,
            outer_width,
            inner_height,
            outer_height,
            angle=0 * u.deg,
            meta=None,
            visual=None,
    ):
        self.center = center

class AsymmetricAnnulusSkyRegion(SkyRegion):
    """Helper class for asymmetric annuli sky regions.

    Used for ellipse and rectangle annuli below.
    """
    _params = (
        "center",
        "inner_width",
        "inner_height",
        "outer_width",
        "outer_height",
        "angle",
    )
    center = ScalarSky("center")
    inner_width = QuantityLength("inner_width")
    outer_width = QuantityLength("outer_width")
    inner_height = QuantityLength("inner_height")
    outer_height = QuantityLength("outer_height")
    angle = QuantityLength("angle")

    def __init__(
            self,
            center,
            inner_width,
            outer_width,
            inner_height,
            outer_height,
            angle=0 * u.deg,
            meta=None,
            visual=None,
    ):

width : `~astropy.units.Quantity`
        The width of the rectangle (before rotation) as an angle
    height : `~astropy.units.Quantity`
        The height of the rectangle (before rotation) as an angle
    angle : `~astropy.units.Quantity`, optional
        The rotation angle of the rectangle, measured anti-clockwise. If set to
        zero (the default), the width axis is lined up with the longitude axis
        of the celestial coordinates.
    meta : `~regions.RegionMeta` object, optional
        A dictionary which stores the meta attributes of this region.
    visual : `~regions.RegionVisual` object, optional
        A dictionary which stores the visual meta attributes of this region.
    """
    _params = ('center', 'width', 'height', 'angle')
    center = ScalarSky('center')
    width = QuantityLength('width')
    height = QuantityLength('height')
    angle = QuantityLength('angle')

    def __init__(self, center, width, height, angle=0 * u.deg, meta=None, visual=None):
        self.center = center
        self.width = width
        self.height = height
        self.angle = angle
        self.meta = meta or {}
        self.visual = visual or {}

    def to_pixel(self, wcs):
        center, scale, north_angle = skycoord_to_pixel_scale_angle(self.center, wcs)
        # FIXME: The following line is needed to get a scalar PixCoord
        center = PixCoord(float(center.x), float(center.y))
        width = self.width.to('deg').value * scale

Used for ellipse and rectangle annuli below.
    """
    _params = (
        "center",
        "inner_width",
        "inner_height",
        "outer_width",
        "outer_height",
        "angle",
    )
    center = ScalarSky("center")
    inner_width = QuantityLength("inner_width")
    outer_width = QuantityLength("outer_width")
    inner_height = QuantityLength("inner_height")
    outer_height = QuantityLength("outer_height")
    angle = QuantityLength("angle")

    def __init__(
            self,
            center,
            inner_width,
            outer_width,
            inner_height,
            outer_height,
            angle=0 * u.deg,
            meta=None,
            visual=None,
    ):
        self.center = center
        self.inner_width = inner_width
        self.outer_width = outer_width

Used for ellipse and rectangle annuli below.
    """
    _params = (
        "center",
        "inner_width",
        "inner_height",
        "outer_width",
        "outer_height",
        "angle",
    )
    center = ScalarSky("center")
    inner_width = QuantityLength("inner_width")
    outer_width = QuantityLength("outer_width")
    inner_height = QuantityLength("inner_height")
    outer_height = QuantityLength("outer_height")
    angle = QuantityLength("angle")

    def __init__(
            self,
            center,
            inner_width,
            outer_width,
            inner_height,
            outer_height,
            angle=0 * u.deg,
            meta=None,
            visual=None,
    ):
        self.center = center
        self.inner_width = inner_width
        self.outer_width = outer_width
        self.inner_height = inner_height

"""Helper class for asymmetric annuli sky regions.

    Used for ellipse and rectangle annuli below.
    """
    _params = (
        "center",
        "inner_width",
        "inner_height",
        "outer_width",
        "outer_height",
        "angle",
    )
    center = ScalarSky("center")
    inner_width = QuantityLength("inner_width")
    outer_width = QuantityLength("outer_width")
    inner_height = QuantityLength("inner_height")
    outer_height = QuantityLength("outer_height")
    angle = QuantityLength("angle")

    def __init__(
            self,
            center,
            inner_width,
            outer_width,
            inner_height,
            outer_height,
            angle=0 * u.deg,
            meta=None,
            visual=None,
    ):
        self.center = center
        self.inner_width = inner_width