Find the Convex Hull of the internal set of x,y points.

        Returns
        -------
         bnodes : array of ints
            indices corresponding to points on the convex hull

def convex_hull(self):
        """
        Find the Convex Hull of the internal set of x,y points.

        Returns
        -------
         bnodes : array of ints
            indices corresponding to points on the convex hull
        """
        bnodes, nb, na, nt = _tripack.bnodes(self.lst, self.lptr, self.lend, self.npoints)
        return self._deshuffle_simplices(bnodes[:nb] - 1)