input: 
  import numpy as np
  
  def generate_voltage_signal(frequency: float, amplitude: float, noise_std_dev: float, duration: float, sampling_rate: int) -> np.ndarray:
      """ Generate a voltage signal with a given frequency and amplitude, 
      and add random Gaussian noise to it.
      >>> generate_voltage_signal(250, 1, 0.1, 1, 1000).shape
      (1000,)
      >>> np.mean(generate_voltage_signal(250, 1, 0.1, 1, 1000))
      0.0
      """
      t = np.linspace(0, duration, int(duration * sampling_rate))
      voltage_signal = amplitude * np.sin(2 * np.pi * frequency * t) + np.random.normal(0, noise_std_dev, len(t))
      return voltage_signal
  
output:     t = np.linspace(0, duration, int(duration * sampling_rate))
      voltage_signal = amplitude * np.sin(2 * np.pi * frequency * t) + np.random.normal(0, noise_std_dev, len(t))
      return voltage_signal