Currently, to set the debug options to true the 'solver_options' structure must contain a field .debug = true. It would be more logical for this field to be included in the 'options' structure instead.
This issue has been fixed as of release 'v0.3.10' (bb8406630ea952b0b5ba63e180d0030f91e8390c), since options are now all handles by the Spcies_options class.
Currently, to set the debug options to true the 'solver_options' structure must contain a field .debug = true. It would be more logical for this field to be included in the 'options' structure instead.