Functions for checks and cleaning in parse_xml

[AdrianDAlessandro]

I'd split all these little checks and bits for cleaning the text into separate functions for readability + testability. For example, this one could be something like this:

def get_year(soup: BeautifulSoup) -> str:
    # Check if the 'accepted' date is found within 'date', and if it contains a 'year' tag
    ### no check for unicode or hexacode or XML tags
    if date := soup.find("date", {"date-type": "accepted"}):
        if year := date.find("year"):
            # Extract the text content of the 'year' tag if found
            return year.text

    # If 'accepted' date or 'year' is missing, return empty string
    return ""

(I'm not saying you have to do that on this PR -- just food for thought)

Originally posted by @alexdewar in #263 (comment)