input: Write a python function to generate a summary using NLTK.
  assert summarize_text("<input> The fox is a small to medium-sized mammal belonging to several genera of the family Canidae. Its coat colour ranges from pale red to very dark brown. The fox lives in almost every biome, but its main territory is the forests of the northern hemisphere. Foxes are omnivores, meaning they eat both plants and animals. They are mainly active at night and often hunt for their food.</input>") == "Foxes are omnivores, meaning they eat both plants and animals. They are mainly active at night and often hunt for their food."
  assert summarize_text("<input> The cat is a small domestic carnivorous mammal with soft fur, a short snout, and retractile claws. It is often valued by humans for companionship and for its ability to hunt vermin. Cats are known to be playful and curious animals.</input>") == "Cats are known to be playful and curious animals."
output: import nltk
  from nltk.tokenize import sent_tokenize
  nltk.download('punkt')
  
  def summarize_text(text):
      start_tag = "<input>"
      end_tag = "</input>"
      
      if text.startswith(start_tag) and text.endswith(end_tag):
          text = text[len(start_tag):-len(end_tag)]
      
      sentences = sent_tokenize(text)
      
      # For simplicity, we will take the last two sentences as the summary
      summary = " ".join(sentences[-2:])
      
      return summary