code: def export_polydata(obj, file_name, **kwargs):
      
      content = export_polydata_str(obj, **kwargs)
      return exch.write_file(file_name, content)
docs: Exports control points or evaluated points in VTK Polydata format.
  
      Please see the following document for details: http://www.vtk.org/VTK/img/file-formats.pdf
  
      Keyword Arguments:
          * ``point_type``: **ctrlpts** for control points or **evalpts** for evaluated points
          * ``tessellate``: tessellates the points (works only for surfaces)
  
      :param obj: geometry object
      :type obj: abstract.SplineGeometry, multi.AbstractContainer
      :param file_name: output file name
      :type file_name: str
      :raises GeomdlException: an error occurred writing the file