SDF error through drake: Unable to read SDF string

drake_sdf_empty_string.py

import sys

from pydrake.multibody.parsing import (
    Parser,
)
from pydrake.multibody.plant import (
    MultibodyPlant,
)

def main() -> None:

  plant = MultibodyPlant(time_step=0.01)
  parser = Parser(plant)

  notknownelement = '';
  parser.AddModelFromString(notknownelement, 'sdf');

if __name__ == '__main__':
    sys.exit(main())