input: 
  def find_strongest_animal(animals):
      """
      This function takes a list of animal names and finds the one with the strongest characteristic 
      based on the number of vowels it contains. A vowel is defined as any of the letters a, e, i, o, u. 
      The strength is calculated by subtracting the number of consonants from the number of vowels. 
      The animal with the highest strength value is considered the strongest. If there is a tie, the 
      function returns the first animal in the list with the highest strength.
      
      :param animals: A list of animal names
      :return: The name of the strongest animal based on the defined characteristic
      
      >>> find_strongest_animal(['Cheetah', 'Lion', 'Tiger'])
      'Tiger'
      >>> find_strongest_animal(['Owl', 'Peacock', 'Eagle'])
      'Eagle'
      """
      def strength(animal):
          vowels = "aeiouAEIOU"
          num_vowels = sum(1 for char in animal if char in vowels)
          num_consonants = sum(1 for char in animal if char.isalpha() and char not in vowels)
          return num_vowels - num_consonants
      
      return max(animals, key=strength)
  
output:     def strength(animal):
          vowels = "aeiouAEIOU"
          num_vowels = sum(1 for char in animal if char in vowels)
          num_consonants = sum(1 for char in animal if char.isalpha() and char not in vowels)
          return num_vowels - num_consonants
      
      return max(animals, key=strength)