def save(self, doc):
        if doc.id:
            return self.update(doc)
        else:
            return self.insert(doc)
def find_files(pattern, root):
  """Return all the files matching pattern below root dir."""
  for path, _, files in os.walk(root):
    for filename in fnmatch.filter(files, pattern):
      yield os.path.join(path, filename)