input: Write a python function to remove vowels from a sentence.
  assert remove_vowels("The quick brown fox jumps over the lazy dog.") == "Th qck brwn fx jmps vr th lzy dg."
  assert remove_vowels("Hello World!") == "Hll Wrld!"
  assert remove_vowels("A quick brown fox.") == " qck brwn fx."
  assert remove_vowels("AEIOUaeiou") == ""
output: def remove_vowels(sentence):
      vowels = "AEIOUaeiou"
      return ''.join(char for char in sentence if char not in vowels)