code: def update(self):
          
  
          with self.lock:
              # Increment revision and commit it.
              self.revision += 1
              self.server.commit(self.revision + 1)
  
              # Unblock all waiting clients.
              self.next_revision_available.set()
              self.next_revision_available.clear()
  
              # Check sessions to see which revision can be removed.
              if self.sessions:
                  lowest_revision = min(
                      session.revision for session in self.sessions.itervalues())
  
                  # Remove all old revision history
                  if lowest_revision == self.revision:
                      self.server.clean(lowest_revision)
  
          # Invoke hooks
          invoke_hooks(self.hooks, "updated", self.revision)
docs: Update this provider. Should be invoked when the server gets updated.
  
          This method will notify all clients that wait for
          `self.next_revision_available`.