input: from typing import List
  
  
  def generate_voltage_signal(frequency: float, amplitude: float, noise_variance: float) -> List[float]:
      """ Generate a voltage signal with a given frequency, amplitude, and added random noise.
      The signal is generated over a period of 1 second with 1000 samples.
      
      >>> generate_voltage_signal(250, 1, 0.1)
      [0.9515026221291815, 1.8675049072210064, 0.07819697441215339, -0.05639410404454942, -1.174926850078579, ...]
      """
      t = np.linspace(0, 1, 1000)
      voltage_signal = amplitude * np.sin(2 * np.pi * frequency * t) + np.random.normal(0, noise_variance, 1000)
      return voltage_signal.tolist()
output:     import numpy as np