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:sub/utils.py
             product   file:sub/work.py
             product   step:./work.py  # wd=sub

file:sub/utils.py
               state = CONFIRMED
             creator   step:./plan.py
                sink   step:./work.py  # wd=sub

file:sub/work.py
               state = CONFIRMED
             creator   step:./plan.py
                sink   step:./work.py  # wd=sub

step:./work.py  # wd=sub
               state = SUCCEEDED
                need = DEFAULT
           using_env = STEPUP_PATH_FILTER [dynamic]
             creator   step:./plan.py
              source   file:sub/utils.py [dynamic]
              source   file:sub/work.py
