parameters: (authority, host=None, require=False)
return_statement: return validated
docstring: Determine if the authority string is valid.
  
      :param str authority:
          The authority to validate.
      :param str host:
          (optional) The host portion of the authority to validate.
      :param bool require:
          (optional) Specify if authority must not be None.
      :returns:
          ``True`` if valid, ``False`` otherwise
      :rtype:
          bool
docstring_summary: Determine if the authority string is valid.
docstring_tokens: Determine if the authority string is valid .
function: def authority_is_valid(authority, host=None, require=False):
      """Determine if the authority string is valid.
  
      :param str authority:
          The authority to validate.
      :param str host:
          (optional) The host portion of the authority to validate.
      :param bool require:
          (optional) Specify if authority must not be None.
      :returns:
          ``True`` if valid, ``False`` otherwise
      :rtype:
          bool
      """
      validated = is_valid(authority, misc.SUBAUTHORITY_MATCHER, require)
      if validated and host is not None:
          return host_is_valid(host, require)
      return validated
function_tokens: def authority_is_valid ( authority , host = None , require = False ) : validated = is_valid ( authority , misc . SUBAUTHORITY_MATCHER , require ) if validated and host is not None : return host_is_valid ( host , require ) return validated