113 reference

   114     "Increases the reference count on the receiver by one. This prevents the

   115      receiver from being destroyed until a matching call to #destroy is made.

   116 

   117      This method must be called whenever Cairo documentation says so, 

   118      check comment on return value for methods returning a Cairo object"

   119 

   120     ^ self subclassResponsibility

   121 

   122     "Created: / 05-03-2016 / 10:31:17 / Jan Vrany <jan.vrany@fit.cvut.cz>"

   123 !

   124