<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def spawn(self, channels, ax):
 """ Spawns a graphical gate that can be used to update the coordinates of the current gate. """

        if _check_spawnable(self.source_channels, channels):
            sgate = self.gate_type(self.verts, ax, channels)
            self.spawn_list.append(sgate)
            return sgate
        else:
            return None