input: Write a function to filter out all the vowels from a given string and return the string with only the consonants. If the given string is empty, return an empty string.
  assert filter_vowels("Hello World!") == "Hll Wrld!"
  assert filter_vowels("Python Programming") == "Pythn Prgrmmng"
  assert filter_vowels("AEIOUaeiou") == ""
  assert filter_vowels("") == ""
output: def filter_vowels(s):
      vowels = "AEIOUaeiou"
      return ''.join([char for char in s if char not in vowels])