input: Write a function to tokenize a given text using NLTK. The function should take a string as input and return a list of tokens.
  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("Hello, world!") == ['Hello', ',', 'world', '!']
  assert tokenize_text("") == []
output: def tokenize_text(text):
      from nltk.tokenize import word_tokenize
      return word_tokenize(text)