code: def read(self, size=None):
      
      if not self._is_open:
        raise IOError('Not opened.')
  
      if self._current_offset < 0:
        raise IOError(
            'Invalid current offset: {0:d} value less than zero.'.format(
                self._current_offset))
  
      if self._file_data is None or self._current_offset >= self._size:
        return b''
  
      if size is None:
        size = self._size
      if self._current_offset + size > self._size:
        size = self._size - self._current_offset
  
      start_offset = self._current_offset
      self._current_offset += size
      return self._file_data[start_offset:self._current_offset]
docs: Reads a byte string from the file-like object at the current offset.
  
      The function will read a byte string of the specified size or
      all of the remaining data if no size was specified.
  
      Args:
        size (Optional[int]): number of bytes to read, where None is all
            remaining data.
  
      Returns:
        bytes: data read.
  
      Raises:
        IOError: if the read failed.
        OSError: if the read failed.