Class OptionParser

OptionContainer --+
                  |
                 OptionParser

Class attributes:
  standard_option_list : [Option]
    list of standard options that will be accepted by all instances
    of this parser class (intended to be overridden by subclasses).

Instance attributes:
  usage : string
    a usage string for your program.  Before it is displayed
    to the user, "%prog" will be expanded to the name of
    your program (self.prog or os.path.basename(sys.argv[0])).
  prog : string
    the name of the current program (to override
    os.path.basename(sys.argv[0])).
  epilog : string
    paragraph of help text to print after option help

  option_groups : [OptionGroup]
    list of option groups in this parser (option groups are
    irrelevant for parsing the command-line, but very useful
    for generating help)

  allow_interspersed_args : bool = true
    if true, positional arguments may be interspersed with options.
    Assuming -a and -b each take a single argument, the command-line
      -ablah foo bar -bboo baz
    will be interpreted the same as
      -ablah -bboo -- foo bar baz
    If this flag were false, that command line would be interpreted as
      -ablah -- foo bar -bboo baz
    -- ie. we stop processing options as soon as we see the first
    non-option argument.  (This is the tradition followed by
    Python's getopt module, Perl's Getopt::Std, and other argument-
    parsing libraries, but it is generally annoying to users.)

  process_default_values : bool = true
    if true, option default values are processed similarly to option
    values from the command line: that is, they are passed to the
    type-checking function for the option's type (as long as the
    default value is a string).  (This really only matters if you
    have defined custom types; see SF bug #955889.)  Set it to false
    to restore the behaviour of Optik 1.4.1 and earlier.

  rargs : [string]
    the argument list currently being parsed.  Only set when
    parse_args() is active, and continually trimmed down as
    we consume arguments.  Mainly there for the benefit of
    callback options.
  largs : [string]
    the list of leftover arguments that we have skipped while
    parsing options.  If allow_interspersed_args is false, this
    list is always empty.
  values : Values
    the set of option values currently being accumulated.  Only
    set when parse_args() is active.  Also mainly for callbacks.

Because of the 'rargs', 'largs', and 'values' attributes,
OptionParser is not thread-safe.  If, for some perverse reason, you
need to parse command-line arguments simultaneously in different
threads, use different OptionParser instances.

parse_args(args : [string] = sys.argv[1:],
           values : Values = None)
-> (values : Values, args : [string])

Parse the command-line options found in 'args' (default:
sys.argv[1:]).  Any errors result in a call to 'error()', which
by default prints the usage message to stderr and calls
sys.exit() with an error message.  On success returns a pair
(values, args) where 'values' is an Values instance (with all
your option values) and 'args' is the list of arguments left
over after parsing options.

_process_args(largs : [string],
                 rargs : [string],
                 values : Values)

Process command-line arguments and populate 'values', consuming
options and arguments from 'rargs'.  If 'allow_interspersed_args' is
false, stop at the first non-option argument.  If true, accumulate any
interspersed non-option arguments in 'largs'.