code: def test_manager_table_validate_expressions(self):
      post_callback = partial(
          self.validate_post,
          expected={
              "id": 1,
              "data": {
                  "expression_schema": {'"a" + "a"': "float"},
                  "errors": {},
                  "expression_alias": {'"a" + "a"': '"a" + "a"'},
              },
          },
      )
  
      message = {
          "id": 1,
          "name": "table1",
          "cmd": "table_method",
          "method": "validate_expressions",
          "args": [['"a" + "a"']],
      }
      manager = PerspectiveManager()
      table = Table(data)
      manager.host_table("table1", table)
      manager._process(message, post_callback)
  
imports: import json
  import time
  import numpy
  import pyarrow
  from datetime import datetime
  from functools import partial
  from pytest import raises
  from perspective import Table, PerspectiveError, PerspectiveManager
label_desc: Use image node_id 29 for calling the TestPerspectiveManager obj's underlying member method code with example usage: obj.test_manager_table_validate_expressions() without return types