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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def sanitize_line(txt: str) -> str: """ Fixes common mistakes with 'new line' signifiers so that they can be recognized """

    for key in LINE_FIXES:
        index = txt.find(key)
        if index > -1:
            txt = txt[:index] + LINE_FIXES[key] + txt[index + len(key):]
    # Fix when space is missing following new line signifiers
    for item in ['BECMG', 'TEMPO']:
        if item in txt and item + ' ' not in txt:
            index = txt.find(item) + len(item)
            txt = txt[:index] + ' ' + txt[index:]
    return txt