input: Write a python function to find the index of the maximum value in a list.
  assert find_peaks([9, 2, 10, 5, 4, 8, 3, 7])==2
  assert find_peaks([1, 3, 7, 2, 5])==2
  assert find_peaks([4, 4, 4, 4])==0
output: def find_peaks(lst):
      return lst.index(max(lst))