in drop_eval.py [0:0]
def normalize(s: str) -> str:
"""Lower text and remove punctuation, articles and extra whitespace."""
s = s.lower()
exclude = set(string.punctuation)
s = "".join(char for char in s if char not in exclude)
s = re.sub(r"\b(a|an|the)\b", " ", s)
s = " ".join(s.split())
return s