Better type checking of solver object in output_cnf()
Better type checking of solver object in output_cnf()

JElchison/Numberjack,JElchison/Numberjack,JElchison/Numberjack,eomahony/Numberjack,eomahony/Numberjack,eomahony/Numberjack,JElchison/Numberjack,eomahony/Numberjack,eomahony/Numberjack,JElchison/Numberjack