input: Write a function to generate a voltage signal with random noise given a frequency and amplitude. The function should return the generated signal.
  def generate_signal(freq, amplitude):
      import numpy as np 
      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.allclose(generate_signal(250, 1) + np.random.normal(0, 0.1, 1000), np.sin(2*np.pi*250*np.linspace(0, 1, 1000)))
output: def generate_signal(freq, amplitude):
      import numpy as np 
      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