This module is the interface to the apex Fortran library by Emmert et al. [2010] [1]. The interface is not documented. Use apexpy.Apex for all conversions and calculations. You can find some documentation of the actual Fortran library in the source file apexsh.f90.

[1]Emmert, J. T., A. D. Richmond, and D. P. Drob (2010), A computationally compact representation of Magnetic-Apex and Quasi-Dipole coordinates with smooth base vectors, J. Geophys. Res., 115(A8), A08322, doi:10.1029/2010JA015326.