Write a function, max_value, that takes in list of numbers as an argument. The function should return the largest number in the list.
Solve this without using any built-in list methods.
You can assume that the list is non-empty.
max_value([4, 7, 2, 8, 10, 9]) # -> 10
max_value([10, 5, 40, 40.3]) # -> 40.3
max_value([-5, -2, -1, -11]) # -> -1
max_value([42]) # -> 42
max_value([1000, 8]) # -> 1000
max_value([1000, 8, 9000]) # -> 9000
max_value([2, 5, 1, 1, 4]) # -> 5