code: def from_shapefile(output, input_shp_files, validate):
      
      input_parser = shapefileparser.ShapefileParser()
      source_model = input_parser.read(input_shp_files[0], validate)
      for f in input_shp_files[1:]:
          source_model.sources.extend(input_parser.read(f, validate).sources)
      if not output:
          output = os.path.splitext(input_shp_files[0])[0]
      shapefileparser.SourceModelParser().write(output + '.xml', source_model)
docs: Convert multiple ESRI Shapefile(s) into a single NRML source model file.