code: def test_mixed_input_error(df):
      with pytest.raises(ValueError) as err_msg:
          px.line(df)
      assert (
          "Plotly Express cannot process wide-form data with columns of different type"
          in str(err_msg.value)
      )
  
imports: import plotly.express
  import plotly.graph_objects
  import pandas
  import numpy
  from plotly.express._core import build_dataframe, _is_col_list
  from pandas.testing import assert_frame_equal
  import pytest
  import warnings
label_desc: Use image node_id 10 for calling a global function with example usage: test_mixed_input_error(df) without return types