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: [-0.397, 34.399, -13.497, -14.222, -35.751, -17.127, 125.508]

11.273