code: def test_get_df():
      dl = DataLoader()
      # Daily data
      data_path = dl.get_data_home(data_dir=None, data_sub_dir="daily")
      df = dl.get_df(
          data_path=data_path, data_name="daily_peyton_manning"
      )
      assert list(df.columns) == [TIME_COL, "y"]
      assert df.shape == (2905, 2)
  
      # Hourly data
      data_path = dl.get_data_home(data_dir=None, data_sub_dir="hourly")
      df = dl.get_df(data_path=data_path, data_name="hourly_parking")
      assert list(df.columns) == [
          "SystemCodeNumber",
          "Capacity",
          "Occupancy",
          "LastUpdated",
      ]
      assert df.shape == (35717, 4)
  
      # Error due to wrong file name
      data_path = dl.get_data_home(data_dir=None, data_sub_dir="daily")
      file_path = os.path.join(data_path, "parking.csv")
      file_names = dl.get_data_names(data_path=data_path)
      with pytest.raises(
          ValueError,
          match=rf"Given file path '{file_path}' is not found. Available datasets "
          rf"in data directory '{data_path}' are \{file_names}\.",
      ):
          dl.get_df(data_path=data_path, data_name="parking")
  
imports: import os
  import re
  import pandas
  import pytest
  from greykite.common.constants import TIME_COL
  from greykite.common.data_loader import DataLoader
  from greykite.common.testing_utils import assert_equal
label_desc: Use image node_id 6 for calling a global function with example usage: test_get_df() without return types