input: Write a function to generate a voltage signal with random noise using a Python script. The function should take the frequency and amplitude of the signal as input parameters and return the generated voltage signal. If the input frequency or amplitude is not provided, the function should use default values of 250 Hz and 1 V, respectively.
  assert np.array_equal(generate_voltage_signal(250, 1)[:5], np.sin(2*np.pi*250*np.linspace(0, 1, 1000)[:5]) + np.random.normal(0, 0.1, 1000)[:5])
  assert np.array_equal(generate_voltage_signal()[:5], np.sin(2*np.pi*250*np.linspace(0, 1, 1000)[:5]) + np.random.normal(0, 0.1, 1000)[:5])
  assert np.array_equal(generate_voltage_signal(500, 2)[:5], np.sin(2*np.pi*500*np.linspace(0, 1, 1000)[:5]) + np.random.normal(0, 0.1, 1000)[:5])
output: def generate_voltage_signal(frequency=250, amplitude=1):
      t = np.linspace(0, 1, 1000)
      signal = amplitude * np.sin(2 * np.pi * frequency * t)
      noise = np.random.normal(0, 0.1, 1000)
      return signal + noise