SDF error through drake: unknown element

drake_sdf_unknown_element.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 = R"""<?xml version="1.0"?>
<sdf version="1.7">
  <model name="robot2">
    <unknownelement>moving_link</unknownelement>
  </model>
</sdf>
""";
  parser.AddModelFromString(notknownelement, 'sdf');

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