<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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)