code: def test_manager_view_expression_schema(self):
      post_callback = partial(
          self.validate_post,
          expected={"id": 2, "data": {"abc": "float"}},
      )
  
      make_view_message = {
          "id": 1,
          "table_name": "table1",
          "view_name": "view1",
          "cmd": "view",
          "config": {"expressions": {"abc": '"a" + "a"'}},
      }
      message = {
          "id": 2,
          "name": "view1",
          "cmd": "view_method",
          "method": "expression_schema",
          "args": [False],
      }
      manager = PerspectiveManager()
      table = Table(data)
      manager.host_table("table1", table)
      manager._process(make_view_message, self.post)
      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 30 for calling the TestPerspectiveManager obj's underlying member method code with example usage: obj.test_manager_view_expression_schema() without return types