This helper class acts as a SAX filter and can be used as recordHandler or
metadataHandler for Net::OAI::Harvester->listRecord() or getRecord()
requests or within a SAX filter chain.
The Handler may be a class name, in which case a new object of that
class is created on instantiation of a DocumentHelper object, or
an existing SAX filter which then will be reused. (In this case it
is your responsibility to use only filters which support the processing
of multiple documents by one instance.)
If the option provideDocumentEvents is set to a true value, the filter
will generate start_document() and end_document() events.
If the (exlusive to the previous) option suppressDocumentEvents is set to
a true value, the filter will stop start_document() and end_document() events
from propagating up the chain.
If the option dontVerifyHandler is set to a true value, class sanity checks
for existing or freshly created ones are skipped.
The option finalizeHook may specify a callback for postprocessing the
result just after an end_document() event has been forwarded. It is
called with two arguments, the handler object and the result of the
forwarded end_document() and should return something suitable for processing