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: [197.73, 206.105, 102.402, 38.741, 116.866, 78.231, 138.568]

125.52