input: Write a python function to check if a word contains any consonants.
  assert is_consonant("hello") == True
  assert is_consonant("aeiou") == False
  assert is_consonant("bcdfg") == True
output: def is_consonant(word):
      vowels = set("aeiouAEIOU")
      for char in word:
          if char.isalpha() and char not in vowels:
              return True
      return False