input: Write a function to filter out all the vowels from a given string.
  
  def filter_vowels(string):
       vowels = ('a', 'e', 'i', 'o', 'u')
       return ''.join(c for c in string if c not in vowels)
  
  assert filter_vowels("hello world")=="hll wrld"
  assert filter_vowels("Python Programming")=="Pythn Prgrmmng"
  assert filter_vowels("AEIOUaeiou")==""
  assert filter_vowels("")==""
  assert filter_vowels("bcdfghjklmnpqrstvwxyz")=="bcdfghjklmnpqrstvwxyz"
output: def filter_vowels(string):
       vowels = ('a', 'e', 'i', 'o', 'u', 'A', 'E', 'I', 'O', 'U')
       return ''.join(c for c in string if c not in vowels)