Andrey,
The bundle probably would not be of much use to you, since the
function takes as input a Sage multivariate polynomial ring element
and outputs a Sage elliptic curve over some field, when all you want
is symbolic expression in Weierstrass normal form.
Do you have a copy of the implementa
I tried to convert
2*x*y^2 + 2*a5*t*x*y - x^2 + (2*a4 - 8*t^3)*x - 1,
where a4, a5, and t are some complex parameters (which I would like to
keep as undetermined parameters), to Weierstrass normal form using
Nagell's algorithm and was not quite successful since some steps near
the end do not finis
