input: Write a function to count the occurrence of each character in the given string. The function should return a dictionary where each key is a character from the string and the value is the count of that character. The function should handle any input string, including special characters and spaces.
  def char_occurrences(a_string):
      char_count = {}
      for char in a_string:
          if char in char_count:
              char_count[char] += 1
          else:
              char_count[char] = 1
      return char_count
  
  assert char_occurrences("Hello, World!")=={'H': 1, 'e': 1, 'l': 3, 'o': 2, ',': 1, ' ': 1, 'W': 1, 'r': 1, 'd': 1, '!': 1}
  assert char_occurrences("Python Programming")=={'P': 2, 'y': 1, 't': 1, 'h': 1, 'o': 2, 'n': 2, ' ': 1, 'r': 2, 'g': 2, 'a': 1, 'm': 2, 'i': 1}
  assert char_occurrences("")=={}
  assert char_occurrences("123321")=={'1': 2, '2': 2, '3': 2}
  assert char_occurrences("aAaA")=={'a': 2, 'A': 2}
output: def char_occurrences(a_string):
      char_count = {}
      for char in a_string:
          if char in char_count:
              char_count[char] += 1
          else:
              char_count[char] = 1
      return char_count