class_docstr: Interface for defining write-related logic.
  
  If you want to write data to something that isn't built-in, subclass this class
  and call :meth:`~ray.data.Dataset.write_datasink`.
class_docstr_tok: ["Interface","for","defining","write-related","logic",".","If","you","want","to","write","data","to","something","that","is","n't","built-in",",","subclass","this","class","and","call",":","meth",":","`","~ray.data.Dataset.write_datasink","`","."]
docstr: Callback for when a write job starts.
  
  Use this method to perform setup for write tasks. For example, creating a
  staging bucket in S3.
docstr_tok: ["Callback","for","when","a","write","job","starts",".","Use","this","method","to","perform","setup","for","write","tasks",".","For","example",",","creating","a","staging","bucket","in","S3","."]
code: def on_write_start(self) -> None:
      """Callback for when a write job starts.
  
      Use this method to perform setup for write tasks. For example, creating a
      staging bucket in S3.
      """
      pass
  
file_path: ray/python/ray/data/datasource/datasink.py
imports: from typing import Any, Iterable, List
  from ray.data._internal.execution.interfaces import TaskContext
  from ray.data.block import Block
  from ray.util.annotations import DeveloperAPI
label_desc: Use image node_id 1 for calling the Datasink obj's underlying member method code with example usage: obj.on_write_start() without return types