Create a one element tuple

The function one_element_tuple currently returns the value None. Modify it to return a tuple containing just 1 element, the one passed as a parameter:

one_element_tuple('a')  # ('a', )
one_element_tuple(9)    # (9, )
import unittest


class OneElementTupleTestCase(unittest.TestCase):

    def test_tuple_is_correct(self):
        self.assertEqual(one_element_tuple('b'), ('b', ))
        self.assertEqual(one_element_tuple(7), (7, ))