input: Write a function to generate n-grams of the given text with a specified window size. Return the n-grams as a Counter object.
  
  from collections import Counter
  
  def generate_ngrams(text, window_size):
      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)
  
  text = "The quick brown fox jumps over the lazy dog"
  window_size = 3
  
  ngrams_count = generate_ngrams(text, window_size)
  
  assert ngrams_count == Counter({
      'the quick brown': 3,
      'quick brown fox': 2,
      'over the lazy': 1,
      'brown fox jumps': 1,
      'fox jumps over': 1,
      'the lazy dog': 1,
      'jumps over the': 1,
      'quick brown fox jumps': 1
  })
  assert generate_ngrams("a b c d", 2) == Counter({'a b': 1, 'b c': 1, 'c d': 1})
  assert generate_ngrams("a a a", 1) == Counter({'a': 3})
  assert generate_ngrams("", 3) == Counter()
  assert generate_ngrams("a b c d", 5) == Counter()
output: def generate_ngrams(text, window_size):
      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)