relax heading parser to address incorrect styles in document

        return matches.group(0)

    return ""

def is_heading(txt :str):

    '''

    Returns true if text is a heading, i.e. the text starts with 'A.'

    (Previously this predicate was used: ("Heading" in line.style.name) but 

    not all headings have the correct style

    '''

    return txt.startswith("A.")

def parse_all_examples(txt):

    '''

    Parses TOSCA examples. Txt is a list of Docx items (Paragraph, etc.).

    i = 1

    clause = ""

    for line in txt:

        if isinstance(line, Paragraph):

            linetext = str(line.text)

            if "Heading" in line.style.name:

            if is_heading(linetext):

                clause = linetext.split("\t")[0]

                i = 1

        elif isinstance(line, str):