The ChangeRing function enables the changing of the polynomial ring over which a module is defined.
Given an R-module M, where R is a polynomial ring, and another polynomial ring S, construct the S-module N obtained by coercing the coefficients of the elements of the basis and relations of M into S. It is necessary that all elements of the old coefficient ring R can be automatically coerced into the new coefficient ring S. Note that S itself must be polynomial ring having the same rank as R, so S does not specify the new ring for the underlying coefficients (one can use ChangeRing for polynomial rings to do that first).