input: Write a function to generate n-grams of the given text with a specified window size. If the given text is empty, return an empty Counter. The n-grams should be generated in lowercase and returned as a Counter object.
  
  
  from collections import Counter
  
  def generate_ngrams(text, window_size):
      if not text:
          return Counter()
      text = text.lower().split(' ')
      ngrams = []
      for n in range(window_size, len(text) + 1):
          for i in range(len(text) - n + 1):
              ngrams.append(' '.join(text[i:i + n]))
      return Counter(ngrams)
  
  assert generate_ngrams("The quick brown fox jumps over the lazy dog", 3) == Counter({'the quick brown': 1, 'quick brown fox': 1, 'brown fox jumps': 1, 'fox jumps over': 1, 'jumps over the': 1, 'over the lazy': 1, 'the lazy dog': 1})
  assert generate_ngrams("The quick brown fox jumps over the lazy dog", 2) == Counter({'the quick': 1, 'quick brown': 1, 'brown fox': 1, 'fox jumps': 1, 'jumps over': 1, 'over the': 1, 'the lazy': 1, 'lazy dog': 1})
  assert generate_ngrams("The quick brown fox", 4) == Counter({'the quick brown fox': 1})
  assert generate_ngrams("", 3) == Counter()
  assert generate_ngrams("a a a a", 1) == Counter({'a': 4})
  
output: def generate_ngrams(text, window_size):
      if not text:
          return Counter()
      text = text.lower().split(' ')
      ngrams = []
      for n in range(window_size, len(text) + 1):
          for i in range(len(text) - n + 1):
              ngrams.append(' '.join(text[i:i + n]))
      return Counter(ngrams)