code: def get_markdown_files(self, dir_):
          
          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
docs: Get all the markdown files in a folder, recursively
  
          Args:
              dir_: str, a toplevel folder to walk.