input: from typing import List
  
  def generate_voltage_signal(freq: int, amplitude: float, duration: float, sample_rate: int, noise_level: float) -> List[float]:
      """ Generate a voltage signal with random noise.
      >>> generate_voltage_signal(250, 1, 1, 1000, 0.1)
      array([0.98109967, 0.87538134, 0.94979121, ..., 0.98109967, 0.87538134, 0.94979121])
      """
      t = np.linspace(0, duration, duration * sample_rate)
      signal = amplitude * np.sin(2 * np.pi * freq * t)
      noise = np.random.normal(0, noise_level, signal.shape)
      return signal + noise
output:     import numpy as np