input: Write a function to count the total number of vowels in a given string. Return the count as an integer.
  
  def count_vowels(string): 
      vowels = "aeiou"
      count = 0
      for s in string:
          if s.lower() in vowels:
              count += 1
      return count
  
  assert count_vowels("Hello World") == 3
  assert count_vowels("Python Programming") == 4
  assert count_vowels("Rhythm") == 0
  assert count_vowels("AeIoU") == 5
  assert count_vowels("") == 0
output: def count_vowels(string): 
      vowels = "aeiou"
      count = 0
      for s in string:
          if s.lower() in vowels:
              count += 1
      return count