def _Underride(d, **options):
 if (d is None):
  d = {}
 for (key, val) in options.items():
  d.setdefault(key, val)
 return d

def _Underride ( d , ** options ) : if ( d is None ) : d = { } for ( key , val ) in options . items ( ) : d . setdefault ( key , val ) return d
add key-value pairs to d only if key is not in d .