code: def test_img_encode():
      image_path = os.path.join(os.path.dirname(__file__), "mosaic.png")
      image = imread(image_path)
      assert img_encode(image).startswith("data:image/png;base64")
  
imports: import os
  import json
  import numpy
  import pytest
  import pandas
  from pandas.util.testing import assert_frame_equal
  from matplotlib.pyplot import imread
  from mapboxgl.errors import SourceDataError, DateConversionError
  from mapboxgl.utils import df_to_geojson, geojson_to_dict_list, scale_between, create_radius_stops, create_weight_stops, create_numeric_stops, create_color_stops, img_encode, rgb_tuple_from_str, color_map, height_map, numeric_map, convert_date_columns
label_desc: Use image node_id 17 for calling a global function with example usage: test_img_encode() without return types