Putting atoms object in standard form

I believe I have to put the lattices which are to be used in a solid-state NEB calculation in lower triangular form. From perusing the documentation, it appears that there is a method for a “cell” object to do so (I tried it and it works). As I am not very familiar with ASE, I would like to know how to transform an atoms object (lattice plus atom positions) into standard form. Can anyone offer a simple few lines of code on how to do so?