def atrimboth (a,proportiontocut):
    lowercut = int(proportiontocut*len(a))
    uppercut = len(a) - lowercut
    return a[lowercut:uppercut]
Slices off the passed proportion of items from BOTH ends of the passed
dataset/ETHPy150Open radlab/sparrow/src/main/python/third_party/stats.py/atrimboth