def _ord_to_namespace(n, _max_length=None):
  """Convert a namespace ordinal to a namespace string.

  Converts an int, representing the sequence number of a namespace ordered
  lexographically, into a namespace string.

  >>> _ord_to_namespace(0)
  ''
  >>> _ord_to_namespace(1)
  '-'
  >>> _ord_to_namespace(2)
  '--'
  >>> _ord_to_namespace(3)
  '---'

  Args:
    n: A number representing the lexographical ordering of a namespace.
    _max_length: The maximum namespace length.
  Returns:
    A string representing the nth namespace in lexographical order.
  """
  if _max_length is None:
    _max_length = MAX_NAMESPACE_LENGTH

  length = _LEX_DISTANCE[_max_length - 1]
  if n == 0:
    return ''
  n -= 1
  return (NAMESPACE_CHARACTERS[n / length] +
          _ord_to_namespace(n % length, _max_length - 1))
Convert a namespace ordinal to a namespace string.

  Converts an int, representing the sequence number of a namespace ordered
  lexographically, into a namespace string.

  >>> _ord_to_namespace(0)
  ''
  >>> _ord_to_namespace(1)
  '-'
  >>> _ord_to_namespace(2)
  '--'
  >>> _ord_to_namespace(3)
  '---'

  Args:
    n: A number representing the lexographical ordering of a namespace.
    _max_length: The maximum namespace length.
  Returns:
    A string representing the nth namespace in lexographical order.