code: protected void indexVectorInternal(double[] vector) throws Exception {
  		if (vector.length != vectorLength) {
  			throw new Exception("The dimensionality of the vector is wrong!");
  		}
  		// append the persistent index
  		appendPersistentIndex(vector);
  		// append the ram-based index
  		if (loadIndexInMemory) {
  			vectorsList.add(vector);
  		}
  	}
docs: Append the vectors array with the given vector. The iid of this vector will be equal to the current
  value of the loadCounter.
  
  @param vector
  The vector to be indexed
  @throws Exception
  If the vector's dimensionality is different from vectorLength