code: func (m *mruInventoryMap) Exists(iv *wire.InvVect) bool {
  	m.invMtx.Lock()
  	_, exists := m.invMap[*iv]
  	m.invMtx.Unlock()
  
  	return exists
  }
docs: // Exists returns whether or not the passed inventory item is in the map.
  //
  // This function is safe for concurrent access.