code: def read(self, size=None):
          
          if size is None:
              size = self.size - self.position
          else:
              size = min(size, self.size - self.position)
  
          buf = b""
          while size > 0:
              while True:
                  data, start, stop, offset = self.map[self.map_index]
                  if start <= self.position < stop:
                      break
                  else:
                      self.map_index += 1
                      if self.map_index == len(self.map):
                          self.map_index = 0
              length = min(size, stop - self.position)
              if data:
                  self.fileobj.seek(offset + (self.position - start))
                  buf += self.fileobj.read(length)
              else:
                  buf += NUL * length
              size -= length
              self.position += length
          return buf
docs: Read data from the file.