input: Write a python function to generate a list of 10 random colors using the 'matplotlib color' module.
  assert len(generate_random_colors()) == 10
  assert all(isinstance(color, str) for color in generate_random_colors())
  assert all(color.startswith('#') for color in generate_random_colors())
output: def generate_random_colors():
      import matplotlib.colors as mcolors
      import random
      colors = list(mcolors.CSS4_COLORS.values())
      random_colors = random.sample(colors, 10)
      return random_colors