code: def readinto(self, b):
      b_from_java = self._jfile.read(len(b))
      n_read = len(b_from_java)
      b[:n_read] = b_from_java
      return n_read
  
imports: import io
  import json
  import time
  from typing import Dict, List, Union, Any
  import dateutil.parser
  from hailtop.fs.fs import FS
  from hailtop.fs.stat_result import FileType, FileListEntry, FileStatus
label_desc: Use image node_id 7 for calling the HadoopReader obj's underlying member method code with example usage: obj.readinto(b) and returns: n_read