a nexml object
the name of the level of element desired, see details
logical, see Details
the requested metadata as a data.frame. Additional columns indicate the parent element of the return value.
'level' should be either the name of a child element of a NeXML document (e.g. "otu", "characters"), or a path to the desired element, e.g. 'trees/tree' will return the metadata for all phylogenies in all trees blocks.
If a metadata element has other metadata elements nested within it, the nested metadata are returned as well. A column "Meta" will contain the IDs consolidated from the type-specific LiteralMeta and ResourceMeta columns, and IDs are generated for meta elements that have nested elements but do not have an ID ("blank nodes"). A column "meta" contains the IDs of the parent meta elements for nested ones. This means that the resulting table can be self-joined on those columns.
FALSE, the type-specific "LiteralMeta" and "ResourceMeta"
columns will be retained even if a consolidated "Meta" column is present.
Otherwise, only the consolidated column will be included in the result.
TRUE the values for "property" (LiteralMeta) and
"rel" (ResourceMeta) will be consolidated to "property", and "rel" will be
removed from the result.