code: def find_files(path, filter="*.md"):
          
          if os.path.isfile(path):
              return [path]
  
          if os.path.isdir(path):
              matches = []
              for root, dirnames, filenames in os.walk(path):
                  for filename in fnmatch.filter(filenames, filter):
                      matches.append(os.path.join(root, filename))
              return matches
docs: Finds files with an (optional) given extension in a given path.