Obtains the set of printing attributes for this doc object. If the
returned attribute set includes an instance of a particular attribute
X, the printer must use that attribute value for this doc,
overriding any value of attribute
X in the job's attribute set.
If the returned attribute set does not include an instance
of a particular attribute
X or if null is returned, the printer
must consult the job's attribute set to obtain the value for
attribute
X, and if not found there, the printer must use an
implementation-dependent default value. The returned attribute set is
unmodifiable.
Returns:
Unmodifiable set of printing attributes for this doc, or null
to obtain all attribute values from the job's attribute
set.