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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def export_polydata(obj, file_name, **kwargs):
 """ 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 """

    content = export_polydata_str(obj, **kwargs)
    return exch.write_file(file_name, content)