input: Write a function to generate a prime number sequence using Python. The function should return a list of all prime numbers up to a given positive integer n. If n is less than 2, return an empty list.
  
  def generate_prime_numbers(n): 
      if n < 2:
          return []
      primes = [True for i in range(n + 1)] 
      p = 2
      while (p * p <= n): 
          if (primes[p] == True): 
              for i in range(p * p, n + 1, p): 
                  primes[i] = False
          p += 1
      primes[0] = False
      primes[1] = False
      prime_numbers = [p for p in range(n + 1) if primes[p]]
      return prime_numbers
  
  assert generate_prime_numbers(10)==[2, 3, 5, 7]
  assert generate_prime_numbers(1)==[]
  assert generate_prime_numbers(20)==[2, 3, 5, 7, 11, 13, 17, 19]
  assert generate_prime_numbers(0)==[]
  assert generate_prime_numbers(2)==[2]
output: def generate_prime_numbers(n): 
      if n < 2:
          return []
      primes = [True for i in range(n + 1)] 
      p = 2
      while (p * p <= n): 
          if (primes[p] == True): 
              for i in range(p * p, n + 1, p): 
                  primes[i] = False
          p += 1
      primes[0] = False
      primes[1] = False
      prime_numbers = [p for p in range(n + 1) if primes[p]]
      return prime_numbers