createCollection: Work with a Zorba collection
In omegahat/RXQuery: Bi-directional interface to an XQuery engine

A Zorba Collection object contains zero or more Item objects. These Item objects can "be" (i.e. contain) strings, numbers, URIs, XML nodes/documents, and so on.

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createCollection(name, ..., .nodes = list(...), xmlManager = xmlDataManager())
deleteCollection(..., .ids = list(...), xmlManager = xmlDataManager())
getCollection(colNames, mgr = xmlDataManager())

`xmlManager`
`name`
`...`	not used yet in createCollection but will allow a series of zorba::Item objects to be added to the sole collection being constructed. For deleteCollection, these are the names or collection objects (returned from `createCollection`) identifying the collection to be deleted.
`.nodes`
`.ids`	an alternative way to specify the identitifiers of the collections to be deleted which allows an existing list to be used rather than the "loose" collection of elements via ....
`colNames`	the names of the collection objects to retrieve from the data manager
`mgr`	the XML data manager