python slice
# array[start:stop:step]
# start = include everything STARTING AT this idx (inclusive)
# stop = include everything BEFORE this idx (exclusive)
# step = (can be ommitted) difference between each idx in the sequence
arr = ['a', 'b', 'c', 'd', 'e']
arr[2:] => ['c', 'd', 'e']
arr[:4] => ['a', 'b', 'c', 'd']
arr[2:4] => ['c', 'd']
arr[0:5:2] => ['a', 'c', 'e']
arr[:] => makes copy of arr