Exercise $3$: A function that returns a list of substrings

Write a function substring$($string$\_$original, n$)$ that takes a string parameter string$\_$original, and an integer parameter n$,$ and returns a list containing every possible substrings of string$\_$original of length $n.$

Include the following function calls:

print$($substring$("$Hippopotamus$",2))$

# You should see $[\text{'}$Hi$\text{'},\text{'}$ip$\text{'},\text{'}$pp$\text{'},\text{'}$po$\text{'},\text{'}$op$\text{'},\text{'}$po$\text{'},\text{'}$ot$\text{'},\text{'}$ta$\text{'},\text{'}$am$\text{'},\text{'}$mu$\text{'},\text{'}$us$\text{'}]$

print$($substring$("$Abcdefg$",4))$

# You should see $[\text{'}$Abcd$\text{'},$ 'bcde', 'cdef', 'defg'$]$