':param ids: optionally return only ids (and sequences) that are in this list.
Optional: defaults to None (provide all ids)
:type ids: list or None'

def __init__(self, source, ids=None, **kwargs):

    source = bx_seq.twobit.TwoBitFile(source)
    super(FastaDataProvider, self).__init__(source, **kwargs)
    self.ids = (ids or self.source.keys())
