what am I missing?

flatMap.py

#! /usr/bin/env python

from itertools import chain
from functools import partial
from nose.tools import ok_, eq_

def flatMap1(m, f):
    m = [f(i) for i in m if f(i)]
    return reduce(lambda acc,n: acc + n, m, [])

def flatMap2(m, f):
    return list(chain(*map(f, m)))

def flatMap3(m, f):
    return sum(map(f, m), [])

def f(x):
    try:
        return [int(x)]
    except:
        return []

def f2(x):
    try:
        return int(x)
    except:
        return None

# something
class MList(list):
    def __init__(self, l):
        if not isinstance(l, list):
            l = [l]

        super(MList, self).__init__(l)

    def map(self, f):
        return self.flatMap(lambda x: self.__class__(f(x)))

    def flatten(self):
        return self.flatMap(lambda x: x)

    def flatMap(self, f):
        l = []

        for i in self:
            x = f(i)
            if x:
                l.append(x[0])

        return l

eq_(MList([1,2,3]), [1,2,3])


#########################################################################

m = ["1","2a","3"]
result = [1, 3]

eq_(map(f, m), [[1], [], [3]])

for i in [flatMap1, flatMap2, flatMap3]:
    try:
        eq_(i(m, f) , result)
    except AssertionError as e:
        import traceback
        print i
        print traceback.format_exc()


try:
    eq_(MList(m).flatMap(f), result)
except:
    import traceback
    print MList.flatMap
    print traceback.format_exc()

try:
    eq_(MList(m).map(f2), [1, None, 3])
except:
    import traceback
    print MList.map
    print traceback.format_exc()

try:
    eq_(MList([[1], [], [3]]).flatten(), [1, 3])
except:
    import traceback
    print MList.map
    print traceback.format_exc()