ooad1-10  Exercise 2: Reverse-Engineering the Bike Shop
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ex2.py (needs roundtrip.py, uml2py.py and pyreverse; run from the chapter folder):

  """Exercise 2: reverse-engineer the bike shop code and list what the recovered diagram lost. Run from the chapter folder:  py ex2/ex2.py"""
  import pathlib
  import sys

  HERE = pathlib.Path(__file__).resolve().parent.parent
  sys.path.insert(0, str(HERE))
  import roundtrip  # noqa: E402

  print(roundtrip.compare(HERE / "ex1" / "shop.mmd", HERE / "ex1" / "shop_generated.py", HERE / "ex2" / "rt"))
  print()
  print("what pyreverse drew for the classes (excerpt):")
  text = (HERE / "ex2" / "rt" / "classes_rt.mmd").read_text(encoding="utf8")
  for line in text.splitlines():
      if "-->" in line or "--*" in line or "--o" in line or "--|>" in line or "list[" in line or "*" in line:
          print("   " + line.strip())

Run with:  py ex2/ex2.py

Output:

  design: 7 classes, 4 relationships | recovered from the code: 3
     in the design, NOT recovered : RepairJob has JobPart
     in the design, NOT recovered : StandardPricing realises Pricing
     recovered, NOT in the design : RepairJob has JobStatus
     recovered                    : JobPart has Part
     recovered                    : RepairJob has Bike

  what pyreverse drew for the classes (excerpt):
     job_parts : list[JobPart]
     total(pricing: Pricing)* int
     price(hours: float, part_pence: int)* int
     RepairJob --> Bike : bike
     RepairJob --> JobStatus : status
     JobPart --> Part : part

WHAT WAS LOST, AND WHOSE LIMIT IT IS
  RepairJob has JobPart (composition): lost. The code holds a list[JobPart], and pyreverse shows it only as the text of a field, not as an arrow. This is the TOOL's limit: the information (a list of JobPart objects) is in the code.
  StandardPricing realises Pricing: lost. The code never says so (Pricing is a Protocol and StandardPricing just has a matching method). This is the CODE's limit: nothing in the source names the relationship, so no tool could recover it. It is also a trade-off of Python's structural typing.
  Multiplicities, and the fact that JobPart belongs to exactly one job: not in the code at all (CODE).
GAINED
  RepairJob has JobStatus: pyreverse reads the attribute 'status: JobStatus' as an association. The design drew it as an attribute; both are valid ways to show the same fact.
Also visible in the excerpt: pyreverse marks total() and price() with * (abstract), because their generated bodies only raise NotImplementedError. That is a misreading, so a reverse-engineered diagram of stub code needs reading with care.

WHY THIS WORKS AS AN ANSWER
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Sorting each loss into 'tool' or 'code' matters: a tool limit might be fixed by another tool or by annotations, a code limit cannot be recovered by any tool and must live in a hand-written diagram or a note.