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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_markdown_files(self, dir_):
 """ Get all the markdown files in a folder, recursively Args: dir_: str, a toplevel folder to walk. """

        md_files = OrderedSet()
        for root, _, files in os.walk(dir_):
            for name in files:
                split = os.path.splitext(name)
                if len(split) == 1:
                    continue
                if split[1] in ('.markdown', '.md', '.yaml'):
                    md_files.add(os.path.join(root, name))
        return md_files