input: Write a function to remove all vowels from a given string. The function should return the modified string after filtering out the vowels. If the input string is empty, the function should return an empty 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")=="hll"
  assert filter_vowels("algorithm")=="lgrthm"
  assert filter_vowels("python")=="pythn"
  assert filter_vowels("aeiou")==""
  assert filter_vowels("")==""
output: def filter_vowels(string):
       vowels = ('a', 'e', 'i', 'o', 'u')
       return ''.join(c for c in string if c not in vowels)