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(self, bufsize):
      self.tick()
      bufsize = min(5, bufsize)  # truncate the read size
      result = self.data[self.pos : self.pos + bufsize]
      self.pos += len(result)
      return result
  
label_desc: Use image node_id 3 for calling the MockSocket obj's underlying member method code with example usage: obj.recv(bufsize) and returns: result