  We present the study of a sample of seven "bare" active galactic nuclei (AGN)
observed with Suzaku. We interpret the spectrum of these sources with a
relativistic reflection component and we employ our model RELXILL_NK to test
the Kerr nature of their supermassive black holes. We constrain the Johannsen
deformation parameters $\alpha_{13}$ and $\alpha_{22}$, in which the Kerr
metric is recovered when $\alpha_{13} = \alpha_{22} = 0$. All our measurements
are consistent with the hypothesis that the spacetime geometry around these
supermassive objects is described by the Kerr solution. For some sources, we
obtain quite strong constraints on $\alpha_{13}$ and $\alpha_{22}$ when
compared to those found in our previous studies. We discuss the systematic
uncertainties in our tests and the implications of our results.
