class_docstr: A subclass of :class:`~ffcv.fields.Field` supporting variable-length byte
  arrays.
  
  Intended for use with data such as text or raw data which may not have a
  fixed size. Data is written sequentially while saving pointers and read by
  pointer lookup.
  
  The writer expects to be passed a 1D uint8 numpy array of variable length for each sample.
class_docstr_tok: ["A","subclass","of",":","class",":","`","~ffcv.fields.Field","`","supporting","variable-length","byte","arrays",".","Intended","for","use","with","data","such","as","text","or","raw","data","which","may","not","have","a","fixed","size",".","Data","is","written","sequentially","while","saving","pointers","and","read","by","pointer","lookup",".","The","writer","expects","to","be","passed","a","1D","uint8","numpy","array","of","variable","length","for","each","sample","."]
code: def __init__(self):
      pass
  
imports: from typing import Callable, TYPE_CHECKING, Tuple, Type
  from dataclasses import replace
  import numpy
  from .base import Field, ARG_TYPE
  from ..pipeline.operation import Operation
  from ..pipeline.state import State
  from ..pipeline.compiler import Compiler
  from ..pipeline.allocation_query import AllocationQuery
  from ..libffcv import memcpy
label_desc: Use image node_id 1 to create a new BytesField object from inherited base classes: Field with example: obj = BytesField()