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