input: Write a python function to count the occurrences of each character in a given string.
  assert char_count("hello") == {'h': 1, 'e': 1, 'l': 2, 'o': 1}
  assert char_count("testcase") == {'t': 2, 'e': 2, 's': 2, 'c': 1, 'a': 1}
  assert char_count("aabbcc") == {'a': 2, 'b': 2, 'c': 2}
output: def char_count(s):
      counts = {}
      for char in s:
          if char in counts:
              counts[char] += 1
          else:
              counts[char] = 1
      return counts