code: def test_vectors_extend():
      vs = vectors()
      vs.extend([vector([1, 2, 3]), vector([4, 5, 6])])
      assert len(vs) == 2
  
imports: from dlib import vector, vectors, vectorss, dot
  from pytest import raises
label_desc: Use image node_id 16 for calling a global function with example usage: test_vectors_extend() without return types