Citations and answer grounding

import re

sections = {f"s{i + 1}": p.strip() for i, p in enumerate(re.split(r"\n(?=## )", PROTOCOL)[1:])}

answer = [   # (claim, section it cites)
    ("Check eGFR at least once a year.", "s2"),
    ("Do not start metformin if eGFR is below 45.", "s2"),
    ("Stop metformin if eGFR falls below 30.", "s4"),          # right fact, wrong citation
    ("Metformin can be continued at any eGFR above 15.", "s2"),  # unsupported claim
    ("Start metformin if eGFR is below 45.", "s2"),             # reverses the rule
]

STOP = {"the", "a", "an", "is", "if", "at", "of", "to", "and", "or", "be", "can", "any", "do", "not"}

def content_words(text):
    return {w for w in re.findall(r"[a-z0-9]+", text.lower()) if w not in STOP}

def support(claim, source_text):
    """Share of the claim's content words, and all of its numbers, found in the cited source."""
    words, src = content_words(claim), content_words(source_text)
    numbers_ok = all(n in src for n in re.findall(r"\d+", claim))
    return len(words & src) / len(words), numbers_ok

for claim, cited in answer:
    overlap, numbers_ok = support(claim, sections[cited])
    verdict = "supported" if overlap >= 0.8 and numbers_ok else "CHECK"
    print(f"{verdict:<9} [{cited}] overlap {overlap:.2f} numbers {'ok' if numbers_ok else 'missing'}  {claim}")

# supported [s2] overlap 1.00 numbers ok  Check eGFR at least once a year.
# supported [s2] overlap 0.80 numbers ok  Do not start metformin if eGFR is below 45.
# CHECK     [s4] overlap 0.17 numbers missing  Stop metformin if eGFR falls below 30.
# CHECK     [s2] overlap 0.40 numbers missing  Metformin can be continued at any eGFR above 15.
# supported [s2] overlap 0.80 numbers ok  Start metformin if eGFR is below 45.

def best_source(claim):
    return max(sections, key=lambda sid: support(claim, sections[sid])[0])

for claim, cited in answer:
    overlap, numbers_ok = support(claim, sections[cited])
    if not (overlap >= 0.8 and numbers_ok):
        better = best_source(claim)
        o2, n2 = support(claim, sections[better])
        fix = f"cite {better} instead" if o2 >= 0.8 and n2 else "no section supports it: remove or flag"
        print(f"{claim}\n  -> {fix}")

# Stop metformin if eGFR falls below 30.
#   -> cite s2 instead
# Metformin can be continued at any eGFR above 15.
#   -> no section supports it: remove or flag