input: Write a function to generate a voltage signal with random noise. The function should take frequency and amplitude as parameters, and return the generated voltage signal.
  
  def generate_voltage_signal(freq, amplitude):
      t = np.linspace(0, 1, 1000)
      voltage_signal = np.sin(2*np.pi*freq*t) + np.random.normal(0, 0.1, 1000)
      return voltage_signal
  
  assert np.array_equal(generate_voltage_signal(250, 1).shape, (1000,))
  assert isinstance(generate_voltage_signal(250, 1), np.ndarray)
output: def generate_voltage_signal(freq, amplitude):
      t = np.linspace(0, 1, 1000)
      voltage_signal = amplitude * np.sin(2*np.pi*freq*t) + np.random.normal(0, 0.1, 1000)
      return voltage_signal