input: Write a function to tokenize a given text string using the NLTK library. The function should return a list of tokens generated from the input text. If the input text is empty, the function should return an empty list. 
  
  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('')==[]
  assert tokenize_text('This is a test.')==['This', 'is', 'a', 'test', '.']
output: def tokenize_text(text):
      if not text:
          return []
      from nltk.tokenize import word_tokenize
      return word_tokenize(text)