input: Write a python function to find common keys in two dictionaries.
  assert compare_dictionaries({'a': 1, 'b': 2, 'c': 3}, {'b': 3, 'c': 4, 'd': 5}) == ['b', 'c']
  assert compare_dictionaries({'x': 10, 'y': 20}, {'y': 30, 'z': 40}) == ['y']
  assert compare_dictionaries({'key1': 'value1'}, {'key2': 'value2'}) == []
output: def compare_dictionaries(dict1, dict2):
      return list(set(dict1.keys()) & set(dict2.keys()))