input: Write a function to remove all vowels from a given string. The function should return the string without any vowels. If the input string is empty, it should return an empty string.
  def remove_vowels(string):
      vowels = ['a','e','i','o','u']
      new_string = ''
      for char in string:
          if char.lower() not in vowels:
              new_string += char
      return new_string
  
  assert remove_vowels("hello") == "hll"
  assert remove_vowels("aeiou") == ""
  assert remove_vowels("python") == "python"
  assert remove_vowels("This is a test") == "Ths s  tst"
  assert remove_vowels("") == ""
output: def remove_vowels(string):
      vowels = ['a','e','i','o','u']
      new_string = ''
      for char in string:
          if char.lower() not in vowels:
              new_string += char
      return new_string