input: Write a python function that accepts a string of space-separated lowercase characters and returns a dictionary containing the most frequently occurring characters and their counts. If there are ties in frequency, include all tied characters.
  assert frequency_count('a b b a') == {'a': 2, 'b': 2}
  assert frequency_count('a b c a b') == {'a': 2, 'b': 2}
  assert frequency_count('a b c d g') == {'a': 1, 'b': 1, 'c': 1, 'd': 1, 'g': 1}
  assert frequency_count('r t g') == {'r': 1, 't': 1, 'g': 1}
  assert frequency_count('b b b b a') == {'b': 4}
  assert frequency_count('r t g') == {'r': 1, 't': 1, 'g': 1}
  assert frequency_count('') == {}
  assert frequency_count('a') == {'a': 1}
output: def frequency_count(s):
      from collections import Counter
      counts = Counter(s.split())
      max_count = max(counts.values(), default=0)
      return {ch: cnt for ch, cnt in counts.items() if cnt == max_count}