input: Write a python function to utilize the MultiObjectDict class to store multiple values for the same key and retrieve them.
  ```python
  assert multi_object_dict_example() == {'fruit': ['apple', 'banana', 'cherry'], 'color': ['red', 'blue']}
output: class MultiObjectDict:
      def __init__(self):
          self._dict = {}
  
      def add(self, key, value):
          if key not in self._dict:
              self._dict[key] = []
          self._dict[key].append(value)
  
      def get(self, key):
          return self._dict.get(key, [])
  
  def multi_object_dict_example():
      mod = MultiObjectDict()
      mod.add('fruit', 'apple')
      mod.add('fruit', 'banana')
      mod.add('fruit', 'cherry')
      mod.add('color', 'red')
      mod.add('color', 'blue')
      return {key: mod.get(key) for key in mod._dict}