code: def set_trace_cond(klass, marker='default', cond=None):
          
          tc = klass.trace_counts
          tc[marker] = [cond, 0]
docs: Sets a condition for set_trace statements that have the
              specified marker.  A condition can be either callable, in
              which case it should take one argument, which is the
              number of times set_trace(marker) has been called,
              or it can be a number, in which case the break will
              only be called.