root:
             product   file:plan.py
             product   step:./plan.py

file:plan.py
               state = CONFIRMED
             creator   root:
                sink   step:./plan.py

step:./plan.py
               state = SUCCEEDED
                need = PLAN
           using_env = STEPUP_PATH_FILTER [dynamic]
             creator   root:
              source   file:plan.py
             product   file:demo.py
             product   step:./demo.py

file:demo.py
               state = CONFIRMED
             creator   step:./plan.py
                sink   step:./demo.py

step:./demo.py
               state = SUCCEEDED
                need = DEFAULT
           using_env = STEPUP_PATH_FILTER [dynamic]
             creator   step:./plan.py
              source   file:demo.py
             product   file:subdir/foo.out
                sink   file:subdir/foo.out [dynamic]

file:subdir/foo.out
               state = VOLATILE
             creator   step:./demo.py
              source   step:./demo.py
