code: def test_to_arrow_one_mean(self):
      data = {"a": [1, 2, 3, 4], "b": ["a", "a", "b", "b"]}
  
      table = Table(data)
      view = table.view(
          group_by=["b"], columns=["a"], aggregates={"a": "mean"}
      )
      arrow = view.to_arrow()
  
      table2 = Table(arrow)
      view2 = table2.view()
      result = view2.to_columns()
  
      assert result == {
          "b (Group by 1)": [None, "a", "b"],
          "a": [2.5, 1.5, 3.5],
      }
  
imports: import pyarrow
  from datetime import date, datetime
  from perspective import Table
label_desc: Use image node_id 30 for calling the TestToArrow obj's underlying member method code with example usage: obj.test_to_arrow_one_mean() without return types