code: def convex_hull(self):
          
          if self._faces is None:
              if self._vertices is None:
                  return None
              self.triangulate()
          return self._convex_hull
docs: Return an array of vertex indexes representing the convex hull.
  
          If faces have not been computed for this mesh, the function
          computes them.
          If no vertices or faces are specified, the function returns None.