code: def _emp_extra_options(options):
      
  
      # Check that metadata is valid
      metadata_path = os.path.normpath(os.path.join(options['param_dir'],
                                                    options['metadata']))
      if not os.path.isfile(metadata_path):
          raise IOError, ("Path to metadata file %s is invalid." %
                          metadata_path)
      options['metadata_path'] = metadata_path
  
      # Using subset if given, create and store patch
      subset = options.get('subset', '')
      options['patch'] = emp.Patch(metadata_path, subset)
  
      # If cols or splits not given in options, make empty strings
      if 'cols' not in options.keys():
          options['cols'] = ''
      if 'splits' not in options.keys():
          options['splits'] = ''
  
      return options
docs: Get special options patch, cols, and splits if analysis in emp module