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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 get_filename(self, tag):
        '''Extract and return a documentation filename from a tag.

        Override as necessary, though this default implementation probably
        covers all the cases of interest.

        Args:
            tag: A BeautifulSoup Tag that satisfies match_criterion.

        Returns:
            A string that would be appropriate to use as the documentation
            filename for an entry in a Zeal database.
        '''
        if tag.find('filename', recursive=False) is not None:
            return tag.filename.contents[0]
        elif tag.find('anchorfile', recursive=False) is not None:
            return tag.anchorfile.contents[0] + '#' + tag.anchor.contents[0]