def clean_semver(cls, version_spec):
        return re.sub(r"([<>=~])\s+?v?", "\\1", version_spec, re.IGNORECASE)
def _copy_vars(v_list):
  """Copy variables in v_list."""
  t_list = []
  for v in v_list:
    t_list.append(tf.identity(v))
  return t_list