input: Write a function to count the occurrence of each character in the given string. Return a dictionary where the key is the character and the value is the number of times the character appears in the string.
  
  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': 1, 'y': 1, 't': 1, 'h': 1, 'o': 2, 'n': 2, ' ': 1, 'r': 1, 'g': 3, 'a': 1, 'm': 2, 'i': 1}
  assert char_occurrences("Testing")=={'T': 1, 'e': 2, 's': 1, 't': 2, 'i': 1, 'n': 1, 'g': 1}
  assert char_occurrences("")=={}
  assert char_occurrences("12345")=={'1': 1, '2': 1, '3': 1, '4': 1, '5': 1}
  
  Additional Notes:
  - The function should handle both lowercase and uppercase characters separately.
  - The function should also count spaces and special characters.
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