code: def testEmpty(self):
      gen = VectorInput([])
      der = Derivative()
      p = Pool()
  
      gen.data >> der.signal
      der.signal >> (p, "data")
      run(gen)
  
      self.assertEqualVector(p.descriptorNames(), [])
  
imports: from essentia_test import *
  from essentia.streaming import Derivative
label_desc: Use image node_id 2 for calling the TestDerivative_Streaming obj's underlying member method code with example usage: obj.testEmpty() without return types