def get_links(self, key: MetaKey) -> Sequence[str]:

        try:

            value = self.meta[key]

        except KeyError:

            return ()

        if isinstance(value, str):

            return value.split()

        else:

            raise TypeError("{} metadata is a {}, not str".format(

                key, type(value).__name__,

            ))

class PostingMeta(Metadata):

    """Combined access to posting metadata with its parent transaction metadata

    This lets you access posting metadata through a single dict-like object.

    If you try to look up metadata that doesn't exist on the posting, it will

    look for the value in the parent transaction metadata instead.

    You can set and delete metadata as well. Changes only affect the metadata

    of the posting, never the transaction. Changes are propagated to the

    underlying Beancount data structures.

        for post in self:

            if pred(post):

                try:

                    entity = post.meta['entity']

                except KeyError:

                    pass

                else:

                    if entity not in seen:

                        yield entity

                        seen.add(entity)

    def first_links(self, key: MetaKey, default: Optional[str]=None) -> Iterator[Optional[str]]:

    def make_consistent(self) -> Iterator[Tuple[MetaValue, 'AccrualPostings']]:

        account_ok = isinstance(self.account, str)

        entity_ok = isinstance(self.entity, str)

        # `'/' in self.invoice` is just our heuristic to ensure that the

        # invoice metadata is "unique enough," and not just a placeholder

        # value like "FIXME". It can be refined if needed.

        invoice_ok = isinstance(self.invoice, str) and '/' in self.invoice

        if account_ok and entity_ok and invoice_ok:

            yield (self.invoice, self)

            return

        groups = collections.defaultdict(list)

    meta = data.Metadata({'key': value})

    assert list(meta.get_links('key')) == value.split()

def test_get_links_missing():

    meta = data.Metadata({})

    assert not meta.get_links('key')

@pytest.mark.parametrize('value', testutil.NON_STRING_METADATA_VALUES)

def test_get_links_bad_type(value):

    meta = data.Metadata({'key': value})

    with pytest.raises(TypeError):

        meta.get_links('key')