Fetches all current network names from the client, along with their id.

def refresh(self):
        """
        Fetches all current network names from the client, along with their id.
        """
        if not self._client:
            return
        current_networks = self._client.networks()
        self.clear()
        self.update((net['Name'], net['Id'])
                    for net in current_networks)