code: def test_imshow_dataframe():
      df = px.data.medals_wide(indexed=False)
      fig = px.imshow(df)
      assert fig.data[0].x[0] == df.columns[0]
      assert fig.data[0].x[0] == "nation"
      assert fig.layout.xaxis.title.text is None
      assert fig.data[0].y[0] == df.index[0]
      assert fig.data[0].y[0] == 0
      assert fig.layout.yaxis.title.text is None
  
      df = px.data.medals_wide(indexed=True)
      fig = px.imshow(df)
      assert fig.data[0].x[0] == df.columns[0]
      assert fig.data[0].x[0] == "gold"
      assert fig.layout.xaxis.title.text == df.columns.name
      assert fig.layout.xaxis.title.text == "medal"
      assert fig.data[0].y[0] == df.index[0]
      assert fig.data[0].y[0] == "South Korea"
      assert fig.layout.yaxis.title.text == df.index.name
      assert fig.layout.yaxis.title.text == "nation"
  
imports: import plotly.express
  import numpy
  import pytest
  import xarray
  from PIL import Image
  from io import BytesIO
  import base64
  import datetime
  from plotly.express.imshow_utils import rescale_intensity
label_desc: Use image node_id 19 for calling a global function with example usage: test_imshow_dataframe() without return types