input: def generate_voltage_signal(freq: float, amplitude: float) -> np.ndarray:
      """ Generate a voltage signal with random noise.
      The signal has a given frequency and amplitude. The generated signal is a sine wave 
      with added Gaussian noise.
      >>> generate_voltage_signal(250, 1)
      array([ 0.937..., -0.042..., 0.815..., ...])
      """
      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
output:     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