def is_watertight(self):
        """
        Check if a mesh is watertight by making sure every edge is
        included in two faces.

        Returns
        ----------
        is_watertight : bool
          Is mesh watertight or not
        """
        if self.is_empty:
            return False
        watertight, winding = graph.is_watertight(
            edges=self.edges, edges_sorted=self.edges_sorted)
        self._cache['is_winding_consistent'] = winding
        return watertight
Check if a mesh is watertight by making sure every edge is
        included in two faces.

        Returns
        ----------
        is_watertight : bool
          Is mesh watertight or not