*Additional note
Supplemental explaination of the format of the NET section in the design.def: 
-------------------------------------------------------------------------------
NET
Net_Name1    Type    Inst_Name1.pin1    Inst_Name2.pin2    Inst_Name3.pin3 ....
Net_Name2    Type    Inst_Name5.pin1    Inst_Name6.pin2    Inst_Name7.pin3 ....
 .....
END NET
-------------------------------------------------------------------------------
Each line repersent a net.
Where the first instance name in the line is the driving cell of the net, and 
other instance names in the line are the driven cells of the net. 
For example, the Inst_Name1 is the driving cell of the net Net_Name1, and the
Inst_Name5 is the driving cell of the net Net_Name2.
