import itertools


def sumlist(x):
    """
    sumlist(x)

    Returns the running sum of a list of numbers, x. For example:
    sumlist([1,2,3]) would return [1,3,6].
    """
    try:
        return list(itertools.accumulate(x))
    except TypeError:
        raise TypeError("unsupported argument type for 'sumlist'")