code: def test_layer_encodings():
      chart = alt.LayerChart().encode(x="column:Q")
      assert chart.encoding.x == alt.X(shorthand="column:Q")
  
imports: import io
  import json
  import operator
  import os
  import pathlib
  import tempfile
  import jsonschema
  import pytest
  import pandas
  import altair.vegalite.v5
label_desc: Use image node_id 20 for calling a global function with example usage: test_layer_encodings() without return types