def check_doc_id(txt):
    """ Quickly checks if a document_id is likely to be valid. Return True / False depending on result """
    if len(txt) == 45 and txt[12] == '-' and all(letter in ['a','b','c','d','e','f','0','1','2','3','4','5','6','7','8','9','-'] for letter in txt):
        return True
    else:
        return False