class_docstr: A class simulating an readable socket, optionally raising a
  special exception every other read.
class_docstr_tok: ["A","class","simulating","an","readable","socket",",","optionally","raising","a","special","exception","every","other","read","."]
code: def recv_into(self, buffer, nbytes=0, flags=0):
      self.tick()
      if nbytes == 0:
          nbytes = len(buffer)
      nbytes = min(5, nbytes)  # truncate the read size
      result = self.data[self.pos : self.pos + nbytes]
      self.pos += len(result)
      buffer[: len(result)] = result
      return len(result)
  
label_desc: Use image node_id 4 for calling the MockSocket obj's underlying member method code with example usage: obj.recv_into(buffer, nbytes, flags) and returns: len