code: async def seen(self, tick, source=None):
          '''
          Update the .seen interval and optionally a source specific seen node.
          '''
          await self.set('.seen', tick)
  
          if source is not None:
              seen = await self.snap.addNode('meta:seen', (source, self.ndef))
              await seen.set('.seen', tickync def seen(self, tick, source=None):
          '''
          Update the .seen interval and optionally a source specific seen node.
          '''
          await self.set('.seen', tick)
  
          if source is not None:
              seen = await self.snap.addNode('meta:seen', (source, self.ndef))
              await seen.set('.seen', tick)
docs: Update the .seen interval and optionally a source specific seen node.