def process_pub_date(year, mon, day):
pub_date = None<EOL>if year and re.match("<STR_LIT>", mon):<EOL><INDENT>pub_date = datetime.datetime.strptime(<EOL>f"<STR_LIT>", "<STR_LIT>"<EOL>).strftime("<STR_LIT>")<EOL><DEDENT>elif year:<EOL><INDENT>pub_date = f"<STR_LIT>"<EOL><DEDENT>return pub_date<EOL>
Create pub_date from what Pubmed provides in Journal PubDate entry