Definition: In this task you will be given a list of numbers and you need to find the mean (average) of that list. The mean of a list can be found by summing every number in the list then dividing the result by the size of that list. The output should be rounded to 3 decimal places.
Input: [204.247, 14.861, 25.294, -7.48, -34.313, -43.283, 138.433, 9.437, 123.092, -55.422]

37.487