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Given the following text description, write Python code to implement the functionality described below step by step
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Description:
 <small><i>This notebook was prepared by Donne Martin. Source and license info is on GitHub.</i></small>
Challenge Notebook
Problem
Step1:  Unit Test
The following unit test is expected to fail until you solve the challenge.
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Python Code:
def insertion_sort(data):
    # TODO: Implement me
    pass
Explanation: <small><i>This notebook was prepared by Donne Martin. Source and license info is on GitHub.</i></small>
Challenge Notebook
Problem: Implement insertion sort.
Constraints
Test Cases
Algorithm
Code
Unit Test
Solution Notebook
Constraints
Is a naiive solution sufficient?
Yes
Test Cases
Empty input -> []
One element -> [element]
Two or more elements
Algorithm
Refer to the Solution Notebook.  If you are stuck and need a hint, the solution notebook's algorithm discussion might be a good place to start.
Code
End of explanation
# %load test_insertion_sort.py
from nose.tools import assert_equal
class TestInsertionSort(object):
    def test_insertion_sort(self):
        print('Empty input')
        data = []
        insertion_sort(data)
        assert_equal(data, [])
        print('One element')
        data = [5]
        insertion_sort(data)
        assert_equal(data, [5])
        print('Two or more elements')
        data = [5, 1, 7, 2, 6, -3, 5, 7, -1]
        insertion_sort(data)
        assert_equal(data, sorted(data))
        print('Success: test_insertion_sort')
def main():
    test = TestInsertionSort()
    test.test_insertion_sort()
if __name__ == '__main__':
    main()
Explanation: Unit Test
The following unit test is expected to fail until you solve the challenge.
End of explanation
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