input: Write a python function to count the frequency of words in a given text using a dictionary.
  assert count_word_frequency("Hello world. Hello again.") == {'hello': 2, 'world.': 1, 'again.': 1}
  assert count_word_frequency("Python is great. Python is fun.") == {'python': 2, 'is': 2, 'great.': 1, 'fun.': 1}
  assert count_word_frequency("Test the function with different inputs.") == {'test': 1, 'the': 1, 'function': 1, 'with': 1, 'different': 1, 'inputs.': 1}
output: def count_word_frequency(text):
      words = text.lower().split()
      frequency = {}
      for word in words:
          if word in frequency:
              frequency[word] += 1
          else:
              frequency[word] = 1
      return frequency