python scripting languages

Hello all expertise,

 I have some inquiries that need to clear...may I know about HETVAL Subroutine from TRAST? what are the significant of this subroutine to the programming? and where did i can get the subroutine trast7_tv?How does it works actually?....

I hope somebody willing to help me..thank you in advance..

Regards

Sya_cya