code: def prepare_read(
      self,
      parallelism: int,
      n_per_block: int,
  ) -> List[ReadTask]:
      read_tasks: List[ReadTask] = []
      meta = BlockMetadata(
          num_rows=1,
          size_bytes=n_per_block,
          schema=None,
          input_files=None,
          exec_stats=None,
      )
  
      for _ in range(parallelism):
          read_tasks.append(
              ReadTask(
                  lambda: [[np.ones(n_per_block, dtype=np.uint8)]], meta
              )
          )
      return read_tasks
  
imports: import os
  from typing import List
  import numpy
  import pandas
  import pytest
  import ray
  from ray._private.internal_api import memory_summary
  from ray.data import Dataset
  from ray.data.block import BlockMetadata
  from ray.data.context import DataContext
  from ray.data.datasource import Datasource, ReadTask
  from ray.data.datasource.csv_datasource import CSVDatasource
  from ray.data.tests.util import column_udf, extract_values
  from ray.tests.conftest import *
label_desc: Use image node_id 1 for calling the OnesSource obj's underlying member method code with example usage: obj.prepare_read(parallelism, n_per_block) and returns: read_tasks