code: def export_stl(surface, file_name, **kwargs):
      
      binary = kwargs.get('binary', True)
      if 'binary' in kwargs:
          kwargs.pop('binary')
      content = export_stl_str(surface, binary=binary, **kwargs)
      return exch.write_file(file_name, content, binary=binary)
docs: Exports surface(s) as a .stl file in plain text or binary format.
  
      Keyword Arguments:
          * ``binary``: flag to generate a binary STL file. *Default: True*
          * ``vertex_spacing``: size of the triangle edge in terms of points sampled on the surface. *Default: 1*
          * ``update_delta``: use multi-surface evaluation delta for all surfaces. *Default: True*
  
      :param surface: surface or surfaces to be saved
      :type surface: abstract.Surface or multi.SurfaceContainer
      :param file_name: name of the output file
      :type file_name: str
      :raises GeomdlException: an error occurred writing the file