input: Write a function to generate a Python dictionary that contains the count of the characters in a given string. If the string is empty, return an empty dictionary.
  assert count_chars("Hello World")=={'H': 1, 'e': 1, 'l': 3, 'o': 2, ' ': 1, 'W': 1, 'r': 1, 'd': 1}
  assert count_chars("")=={}
  assert count_chars("aabbcc")=={'a': 2, 'b': 2, 'c': 2}
  assert count_chars("AaBbCc")=={'A': 1, 'a': 1, 'B': 1, 'b': 1, 'C': 1, 'c': 1}
  assert count_chars("1234567890")=={'1': 1, '2': 1, '3': 1, '4': 1, '5': 1, '6': 1, '7': 1, '8': 1, '9': 1, '0': 1}
output: def count_chars(s):
      if not s:
          return {}
      char_count = {}
      for char in s:
          if char in char_count:
              char_count[char] += 1
          else:
              char_count[char] = 1
      return char_count