input: Write a python function to tokenize a given text using nltk's word_tokenize.
  assert tokenize_text('Python is an interpreted, high-level, general-purpose programming language.') == ['Python', 'is', 'an', 'interpreted', ',', 'high-level', ',', 'general-purpose', 'programming', 'language', '.']
  assert tokenize_text('Natural Language Processing with Python.') == ['Natural', 'Language', 'Processing', 'with', 'Python', '.']
  assert tokenize_text('Hello, world!') == ['Hello', ',', 'world', '!']
output: def tokenize_text(text):
      import nltk
      from nltk.tokenize import word_tokenize
      nltk.download('punkt')
      
      return word_tokenize(text)