def border(self, ax, wcs, **kw_mpl_pathpatch):
        """
        Draws the MOC border(s) on a matplotlib axis.

        This performs the projection of the sky coordinates defining the perimeter of the MOC to the pixel image coordinate system.
        You are able to specify various styling kwargs for `matplotlib.patches.PathPatch` 
        (see the `list of valid keywords <https://matplotlib.org/api/_as_gen/matplotlib.patches.PathPatch.html#matplotlib.patches.PathPatch>`__).

        Parameters
        ----------
        ax : `matplotlib.axes.Axes`
            Matplotlib axis.
        wcs : `astropy.wcs.WCS`
            WCS defining the World system <-> Image system projection. 
        kw_mpl_pathpatch
            Plotting arguments for `matplotlib.patches.PathPatch`

        Examples
        --------
        >>> from mocpy import MOC, WCS
        >>> from astropy.coordinates import Angle, SkyCoord
        >>> import astropy.units as u
        >>> # Load a MOC, e.g. the MOC of GALEXGR6-AIS-FUV
        >>> filename = './../resources/P-GALEXGR6-AIS-FUV.fits'
        >>> moc = MOC.from_fits(filename)
        >>> # Plot the MOC using matplotlib
        >>> import matplotlib.pyplot as plt
        >>> fig = plt.figure(111, figsize=(15, 15))
        >>> # Define a WCS as a context
        >>> with WCS(fig, 
        ...         fov=50 * u.deg,
        ...         center=SkyCoord(0, 20, unit='deg', frame='icrs'),
        ...         coordsys="icrs",
        ...         rotation=Angle(0, u.degree),
        ...         projection="AIT") as wcs:
        ...     ax = fig.add_subplot(1, 1, 1, projection=wcs)
        ...     # Call border giving the matplotlib axe and the `~astropy.wcs.WCS` object.
        ...     moc.border(ax=ax, wcs=wcs, alpha=0.5, color="red")
        >>> plt.xlabel('ra')
        >>> plt.ylabel('dec')
        >>> plt.grid(color="black", linestyle="dotted")
        """
        border.border(self, ax, wcs, **kw_mpl_pathpatch)