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   step:echo Hello > test2.txt

(step:echo Hello > test1.txt)
               state = SUCCEEDED
                need = DEFAULT
             product   (file:test1.txt)
                sink   (file:test1.txt)

(file:test1.txt)
               state = BUILT
             creator   (step:echo Hello > test1.txt)
              source   (step:echo Hello > test1.txt)

step:echo Hello > test2.txt
               state = SUCCEEDED
                need = DEFAULT
             creator   step:./plan.py
             product   file:test2.txt
                sink   file:test2.txt

file:test2.txt
               state = BUILT
             creator   step:echo Hello > test2.txt
              source   step:echo Hello > test2.txt
