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: [110.71, 192.878, 202.479, -53.421, -50.55, 123.37, 217.183, 46.469, 129.17]

102.032