1997 Suzuki Esteem power steering pump of carburettor model

I have Suzuki Esteem 1.3 ltr 1998 carburettor model. Why is there a single wire connected to the power steering pump whic has NO motor inside. It is a simple oil pump that is driven by the belt connected to the main pulley of the engine.

What is the role of this wire. What is this meant for?
What if this NOT connected?
Is this a negative wire just to be earthed or is to be connected to something else?
Thanks
shailendra