<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 async def home_z(self, mount: top_types.Mount = None):
 """ Home the two z-axes """

        if not mount:
            axes = [Axis.Z, Axis.A]
        else:
            axes = [Axis.by_mount(mount)]
        await self.home(axes)