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: [20.538, 100.835, -23.197, 207.707, -12.758, 152.97, 190.404]

90.928