input: Write a function to generate a voltage signal with random noise given a frequency and amplitude. The function should return the voltage signal based on a time vector that covers one second with 1000 points. If the frequency or amplitude is zero, return an empty array.
  assert generate_voltage_signal(250, 1).size==1000
  assert generate_voltage_signal(0, 1).size==0
  assert generate_voltage_signal(250, 0).size==0
  assert generate_voltage_signal(500, 2).size==1000
output: def generate_voltage_signal(frequency, amplitude):
      if frequency == 0 or amplitude == 0:
          return []
      time_vector = np.linspace(0, 1, 1000)
      noise = np.random.normal(0, 0.1, 1000)
      voltage_signal = amplitude * np.sin(2 * np.pi * frequency * time_vector) + noise
      return voltage_signal