code: def get_read_tasks(self, parallelism: int):
      def _blocks_generator():
          values = [1] * self.block_size
          columns = {str(i): values for i in range(self.num_columns)}
          for _ in range(self.num_blocks_per_task):
              if self.data_format == "pandas":
                  yield pd.DataFrame(columns)
              elif self.data_format == "simple":
                  assert len(columns) == 1
                  yield columns["0"]
              elif self.data_format == "pyarrow":
                  yield pa.table(columns)
  
      size_bytes = (
          self.num_blocks_per_task
          * self.num_columns
          * self.block_size
          * 8
      )
  
      return parallelism * [
          ReadTask(
              lambda: _blocks_generator(),
              BlockMetadata(
                  num_rows=self.num_blocks_per_task * self.block_size,
                  size_bytes=size_bytes,
                  schema=None,
                  input_files=None,
                  exec_stats=None,
              ),
          )
      ]
  
imports: import argparse
  import json
  import time
  from typing import Dict, List, Any
  import pandas
  import pyarrow
  import numpy
  import ray
  from ray.data.block import BlockMetadata
  from ray.data.context import DataContext, DEFAULT_TARGET_MAX_BLOCK_SIZE
  from ray.data.datasource import Datasource, ReadTask, Reader
label_desc: Use image node_id 3 for calling the BlockReader obj's underlying member method code with example usage: obj.get_read_tasks(parallelism) and returns: unknown