code: def _namespace_to_ord(namespace):
    
    n = 0
    for i, c in enumerate(namespace):
      n += (_LEX_DISTANCE[MAX_NAMESPACE_LENGTH - i- 1] *
            NAMESPACE_CHARACTERS.index(c)
            + 1)
    return n
docs: Converts a namespace string into an int representing its lexographic order.
  
    >>> _namespace_to_ord('')
    ''
    >>> _namespace_to_ord('_')
    1
    >>> _namespace_to_ord('__')
    2
  
    Args:
      namespace: A namespace string.
  
    Returns:
      An int representing the lexographical order of the given namespace string.