13.0.9 `poly_initial_term'
--------------------------

poly_initial_term(F)
     :  It returns the initial term of a polynomial F  with respect to
     the given weight vector.

poly_initial_term(F | WEIGHT=key0,ORDER=key1,V=key2)
     : This function allows optional variables   WEIGHT, ORDER, V

   Description:

     The weight is given by the optional variable weight w.   It returns


   Example:
      poly_initial_term( x^2+y^2-4 |weight=[100,1],v=[x,y]);

