code: def concatenate_data(data_dir: str) -> None:
      """Read in all data and write it to one file."""
      df = pd.concat(
          (
              read_data_one_file(data_dir=data_dir, fname=fname)
              for fname in os.listdir(data_dir)
              if fname != "all_data.csv"
          ),
          ignore_index=True,
      ).sort_values(["mode", "datetime"], ignore_index=True)
      df.to_csv(os.path.join(data_dir, "all_data.csv"), index=False)
  
imports: import os
  import pandas
  import papermill
label_desc: Use image node_id 2 for calling a global function with example usage: concatenate_data(data_dir) without return types