Class MetaMixin

is a constructor for standalone use. You do *not* want to call this when mixing into a Structure.

Overrides: object.__init__

adds metaItem to self under key.

moreAttrs can be additional keyword arguments; these are used by the XML constructor to define formats or to pass extra items to special meta types.

For convenience, this returns the meta container.

removes a meta item from this meta container.

This will not propagate, i.e., getMeta(key) might still return something unless you give propagate=False.

It is not an error do delete an non-existing meta key.

iterates over all meta items this container has.

Each item consists of key, MetaValue. Multiple MetaValues per key may be given.

This will not iterate up, i.e., in general, getMeta will succeed for more keys than what's given here.

yields all MetaValues for key.

This will traverse down all branches necessary to yield, in sequence, all MetaValues reachable by key.

If propagation is enabled, the first meta carrier that has at least one item exhausts the iteration.

(this currently doesn't return an iterator but a sequence; that's an implementation detail, though. You should only assume whatever comes back is iterable)

marks the meta item key, if existing, as original.

This is for when a meta container has copied metadata. DaCHS' default behaviour is that a subsequent addMeta will clear the copied content. Call this method for the key in question to enable adding to copied metadata.