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: [156.146, -88.32, 1.211, 11.366, 216.143, 66.781, 155.255]

74.083