code: def read_sexpr_block(stream, block_size=16384, comment_char=None):
      """
      Read a sequence of s-expressions from the stream, and leave the
      stream's file position at the end the last complete s-expression
      read.  This function will always return at least one s-expression,
      unless there are no more s-expressions in the file.
  
      If the file ends in in the middle of an s-expression, then that
      incomplete s-expression is returned when the end of the file is
      reached.
  
      :param block_size: The default block size for reading.  If an
          s-expression is longer than one block, then more than one
          block will be read.
      :param comment_char: A character that marks comments.  Any lines
          that begin with this character will be stripped out.
          (If spaces or tabs precede the comment character, then the
          line will not be stripped.)
      """
      start = stream.tell()
      block = stream.read(block_size)
      encoding = getattr(stream, "encoding", None)
      assert encoding is not None or isinstance(block, str)
      if encoding not in (None, "utf-8"):
          import warnings
  
          warnings.warn(
              "Parsing may fail, depending on the properties "
              "of the %s encoding!" % encoding
          )
          # (e.g., the utf-16 encoding does not work because it insists
          # on adding BOMs to the beginning of encoded strings.)
  
      if comment_char:
          COMMENT = re.compile("(?m)^%s.*$" % re.escape(comment_char))
      while True:
          try:
              # If we're stripping comments, then make sure our block ends
              # on a line boundary; and then replace any comments with
              # space characters.  (We can't just strip them out -- that
              # would make our offset wrong.)
              if comment_char:
                  block += stream.readline()
                  block = re.sub(COMMENT, _sub_space, block)
              # Read the block.
              tokens, offset = _parse_sexpr_block(block)
              # Skip whitespace
              offset = re.compile(r"\s*").search(block, offset).end()
  
              # Move to the end position.
              if encoding is None:
                  stream.seek(start + offset)
              else:
                  stream.seek(
                      start + len(block[:offset].encode(encoding))
                  )
  
              # Return the list of tokens we processed
              return tokens
          except ValueError as e:
              if e.args[0] == "Block too small":
                  next_block = stream.read(block_size)
                  if next_block:
                      block += next_block
                      continue
                  else:
                      # The file ended mid-sexpr -- return what we got.
                      return [block.strip()]
              else:
                  raise
  
imports: import bisect
  import os
  import pickle
  import re
  import tempfile
  from functools import reduce
  from xml.etree import ElementTree
  from nltk.data import FileSystemPathPointer, PathPointer, SeekableUnicodeStreamReader, ZipFilePathPointer
  from nltk.internals import slice_bounds
  from nltk.tokenize import wordpunct_tokenize
  from nltk.util import AbstractLazySequence, LazyConcatenation, LazySubsequence
label_desc: Use image node_id 8 for calling a global function with example usage: read_sexpr_block(stream, block_size, comment_char) and returns: tokens, list