'Returns a dictionary mapping tags to their tag count.
For example, if the tag count of tag \'foo\' is 23, then
23 bookmarks were annotated with \'foo\'. A different way
to put it is that 23 users used the tag \'foo\' when
bookmarking the URL.'

def get_tags(self):

    total_tags = {}
    for (url, tags, title, comment, timestamp) in self.bookmarks:
        for tag in tags:
            total_tags[tag] = (total_tags.get(tag, 0) + 1)
    return total_tags
