'Returns items of the given ``dictionary``.
Items are returned sorted by keys. The given ``dictionary`` is not
altered by this keyword.
Example:
| ${items} = | Get Dictionary Items | ${D3} |
| ${items} = [\'a\', 1, \'b\', 2, \'c\', 3]'

def get_dictionary_items(self, dictionary):

    ret = []
    for key in self.get_dictionary_keys(dictionary):
        ret.extend((key, dictionary[key]))
    return ret
