input: Write a python function to generate a random 4x8 two-dimensional array with each cell containing a float number between 0 and 1.
  assert len(random_array()) == 4
  assert all(len(row) == 8 for row in random_array())
  assert all(0 <= cell <= 1 for row in random_array() for cell in row)
output: import random
  
  def random_array():
      return [[random.uniform(0, 1) for _ in range(8)] for _ in range(4)]