  We present the public release version of relxill_nk, an X-ray reflection
model for testing the Kerr hypothesis and general relativity. This model
extends the relxill model that assumes the black hole spacetime is described by
the Kerr metric. We also present relxilllp_nk, the first non-Kerr X-ray
reflection model with a lamppost corona configuration, as well as all other
models available in the full relxill_nk package. In all models the relevant
relativistic effects are calculated through a general relativistic ray-tracing
code that can be applied to any well-behaved, stationary, axisymmetric, and
asymptotically flat black hole spacetime. We show that the numerical error
introduced by using a ray-tracing code is not significant as compared with the
observational error present in current X-ray reflection spectrum observations.
In addition, we present the reflection spectrum for the Johannsen metric as
calculated by relxill_nk.
