input: Write a function to generate a voltage signal with random noise based on the given frequency and amplitude. The function should return the noisy voltage signal as a numpy array.
  
  assert np.array_equal(generate_noisy_signal(250, 1).shape, (1000,))
  assert np.all(generate_noisy_signal(250, 1) != np.sin(2*np.pi*250*np.linspace(0, 1, 1000)))
  assert np.all(generate_noisy_signal(500, 2) == 2 * np.sin(2*np.pi*500*np.linspace(0, 1, 1000)) + np.random.normal(0, 0.1, 1000))
output: import numpy as np
  
  def generate_noisy_signal(frequency, amplitude):
      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