# bifurcate_by.py

# bifurcate_by.py

def bifurcate_by(lst, fn):
    t = [[],[]]
    for x in lst:
        if x[0] == 'b':
            t[0] += [x]
        else:
            t[1] += [x]
    return t

t = bifurcate_by(['beep', 'boop', 'foo', 'bar'], lambda x: x[0] == 'b')
print(t)
# [ ['beep', 'boop', 'bar'], ['foo'] ]