Generate a class diagram of an EBike according to these specifications:
The EBike is composed of a frame (made out of steel), a drive system, and a controller.
Two wheels are inserted into each frame. The drive system is composed of a motor.
Each EBike can be connected to a removable battery. The battery has a stored energy
measured in Watt-hours (Wh). The controller can be in one of three states: On, Off, and
Charging. It also controls the battery, if one is connected, and commands the drive
system. The company plans two different variants of the controller, a basic controller,
and an advanced controller. The advanced controller should be able to estimate the
next Date the bike should be inspected for maintenance.