input: def generate_voltage_signal(freq: float, amplitude: float) -> np.ndarray:
      """Generate a voltage signal with random noise. The signal is a sin wave with the given frequency and amplitude, plus a normal distributed noise.
      
      >>> generate_voltage_signal(250, 1).size
      1000
      >>> np.amax(generate_voltage_signal(250, 1)) > 1.5
      True
      >>> np.amin(generate_voltage_signal(250, 1)) < 0.5
      True
      """
      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