input: Write a python function to count the frequency of each character in a given string.
  assert char_count("Hello World!") == {'H': 1, 'e': 1, 'l': 3, 'o': 2, ' ': 1, 'W': 1, 'r': 1, 'd': 1, '!': 1}
  assert char_count("Python") == {'P': 1, 'y': 1, 't': 1, 'h': 1, 'o': 1, 'n': 1}
  assert char_count("aabbcc") == {'a': 2, 'b': 2, 'c': 2}
output: def char_count(s):
      freq = {}
      for char in s:
          if char in freq:
              freq[char] += 1
          else:
              freq[char] = 1
      return freq