  We present a framework for the solution of Boltzmann's equation in the swarm
limit for arbitrary mass ratio, allowing for solutions of electron or ion
transport. An arbitrary basis set can be used in the framework, which is
achieved by using appropriate quadratures to obtain the required matrix
elements. We demonstrate an implementation using Burnett functions and
benchmark the calculations using Monte-Carlo simulations. Even though the
convergence in transport quantities is always good, the particle distributions
did not always converge, highlighting that simple benchmarks can give
misleading confidence in a choice of basis. We postulate a different basis,
which avoids a spherical harmonic expansion, which is better suited to strong
electric fields or sharp features such as low-energy attachment processes.
