lmap.is_lazy(k) yields True if the given k is lazy and unmemoized in the given lazy map,
        lmap, otherwise False.

def is_lazy(self, k):
        '''
        lmap.is_lazy(k) yields True if the given k is lazy and unmemoized in the given lazy map,
        lmap, otherwise False.
        '''
        v = ps.PMap.__getitem__(self, k)
        if not isinstance(v, (types.FunctionType, partial)) or \
           id(v) in self._memoized or \
           [] != getargspec_py27like(v)[0]:
            return False
        else:
            return True