input: Write a function to generate a voltage signal with random noise using a Python script. The function should take the frequency and amplitude as inputs and return the noisy voltage signal. If the frequency or amplitude is not provided, the function should use default values of 250 Hz and 1 V respectively.
  assert generate_voltage_signal(250, 1).shape == (1000,)
  assert generate_voltage_signal().shape == (1000,)
  assert generate_voltage_signal(500, 2).shape == (1000,)
output: def generate_voltage_signal(frequency=250, amplitude=1):
      import numpy as np
      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