code: def test_mix(self):
      file_path = os.path.join(self.resource_path, "orca/data/csv")
      data_shard = bigdl.orca.data.pandas.read_csv(
          file_path, header=0, names=["user", "item"], usecols=[0, 1]
      )
      data = data_shard.collect()
      df = data[0]
      assert "user" in df.columns
      assert "item" in df.columns
      with self.assertRaises(Exception) as context:
          data_shard = bigdl.orca.data.pandas.read_csv(
              file_path,
              header=0,
              names=["ID", "location"],
              usecols=["ID"],
          )
          data = data_shard.collect()
      self.assertTrue(
          "Passed names did not match usecols" in str(context.exception)
      )
      data_shard = bigdl.orca.data.pandas.read_csv(
          file_path,
          header=0,
          names=["user", "item"],
          usecols=[0, 1],
          dtype={0: np.float32, 1: np.int32},
      )
      data = data_shard.collect()
      df2 = data[0]
      assert df2.user.dtype == "float32" and df2.item.dtype == "int32"
  
      data_shard = bigdl.orca.data.pandas.read_csv(
          file_path,
          header=0,
          names=["user", "item", "location"],
          usecols=[1, 2],
      )
      data = data_shard.collect()
      df2 = data[0]
      assert "user" not in df2.columns
      assert "item" in df2.columns
      assert "location" in df2.columns
  
      data_shard = bigdl.orca.data.pandas.read_csv(
          file_path,
          header=0,
          names=["user", "item", "rating"],
          usecols=["user", "item"],
          dtype={0: np.float32, 1: np.int32},
      )
      data = data_shard.collect()
      df2 = data[0]
      assert df2.user.dtype == "float32" and df2.item.dtype == "int32"
  
      with self.assertRaises(Exception) as context:
          data_shard = bigdl.orca.data.pandas.read_csv(
              file_path,
              header=0,
              names=["user", "item"],
              usecols=[0, 1],
              dtype={1: np.float32, 2: np.int32},
          )
          data = data_shard.collect()
          print(len(data))
      self.assertTrue(
          "column index to be set type is not in current dataframe"
          in str(context.exception)
      )
  
imports: import os.path
  import pytest
  from unittest import TestCase
  import bigdl.orca.data
  import bigdl.orca.data.pandas
  from bigdl.orca.data import SharedValue
  from bigdl.dllib.nncontext import *
  from bigdl.orca.data.transformer import *
  from bigdl.orca import init_orca_context
label_desc: Use image node_id 23 for calling the TestSparkXShards obj's underlying member method code with example usage: obj.test_mix() without return types