'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.
If simplify
is 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.
Also, if simplify
is TRUE
the values for "property" (LiteralMeta) and
"rel" (ResourceMeta) will be consolidated to "property", and "rel" will be
removed from the result.