10 print "<<< ref#(btrack)=", sys.getrefcount(btrack)
    11 bstep= btrack.GetStep2()
    12 print "<<< ref#(btrack, bstep)=",\
    13       sys.getrefcount(btrack),\
    14       sys.getrefcount(bstep)
    16 print "<<< delete bstep"    17 print "<<< ref#(btrack)=", sys.getrefcount(btrack)
    21 cstep= btrack.GetStep2()
    23 print "<<< previous step is still remain?"    27 print "--- stderr ---"