code: def test_melt_projection_pd_7747() -> None:
      df = pl.LazyFrame(
          {
              "number": [1, 2, 1, 2, 1],
              "age": [40, 30, 21, 33, 45],
              "weight": [100, 103, 95, 90, 110],
          }
      )
      result = (
          df.with_columns(pl.col("age").alias("wgt"))
          .melt(id_vars="number", value_vars="wgt")
          .select("number", "value")
          .collect()
      )
      expected = pl.DataFrame(
          {
              "number": [1, 2, 1, 2, 1],
              "value": [40, 30, 21, 33, 45],
          }
      )
      assert_frame_equal(result, expected)
  
imports: import polars
  import polars.selectors
  from polars.testing import assert_frame_equal
label_desc: Use image node_id 2 for calling a global function with example usage: test_melt_projection_pd_7747() without return types