'Append schema object\'s from B{s}ource list to
the B{d}estination list while applying the filter.
@param d: The destination list.
@type d: list
@param s: The source list.
@type s: list
@param filter: A filter that allows items to be appended.
@type filter: L{Filter}'

@classmethod
def append(cls, d, s, filter=Filter()):

    for item in s:
        if (item in filter):
            d.append(item)
