code: def validate_instance(cls, opts):
      
      if opts.loop and (not opts.v2 or opts.v1):
        raise OptionsError('The --loop option only works with @console_rules, and thus requires '
                           '`--v2 --no-v1` to function as expected.')
      if opts.loop and not opts.enable_pantsd:
        raise OptionsError('The --loop option requires `--enable-pantsd`, in order to watch files.')
  
      if opts.v2_ui and not opts.v2:
        raise OptionsError('The --v2-ui option requires --v2 to be enabled together.')
docs: Validates an instance of global options for cases that are not prohibited via registration.
  
      For example: mutually exclusive options may be registered by passing a `mutually_exclusive_group`,
      but when multiple flags must be specified together, it can be necessary to specify post-parse
      checks.
  
      Raises pants.option.errors.OptionsError on validation failure.