code: def mock_load_data_func(x_range, y_range):
      global df
      if df is None:
          xs = np.random.normal(loc=0, scale=500000, size=10000000)
          ys = np.random.normal(loc=0, scale=500000, size=10000000)
          df = pd.DataFrame(dict(x=xs, y=ys))
  
      return df.loc[
          df["x"].between(*x_range) & df["y"].between(*y_range)
      ]
  
file_path: datashader/datashader/tests/test_tiles.py
imports: from __future__ import annotations
  import datashader
  import datashader.transfer_functions
  from datashader.colors import viridis
  from datashader.tiles import render_tiles
  from datashader.tiles import gen_super_tiles
  from datashader.tiles import _get_super_tile_min_max
  from datashader.tiles import calculate_zoom_level_stats
  from datashader.tiles import MercatorTileDefinition
  import numpy
  import pandas
label_desc: Use image node_id 1 for calling a global function with example usage: mock_load_data_func(x_range, y_range) and returns: df