an ``int`` or a ``Dataset`` object containing (at a minimum) a
(0000,0900) *Status* element. If returning a Dataset object then
it may also contain optional elements related to the Status (as in
DICOM Standard Part 7, Annex C).
dataset : pydicom.dataset.Dataset or None
If the status category is 'Success' or 'Warning' then a dataset
containing elements matching the request's Attribute List
conformant to the specifications in the corresponding Service
Class.
If the status is not 'Successs' or 'Warning' then return None.
"""
# User defined function to generate the required attribute list dataset
# implementation is outside the scope of the current example
# We pretend it returns a pydicom Dataset
dataset = create_attribute_list(attr)
# If Display System Management returns an attribute list then the
# SOP Class UID and SOP Instance UID must always be as given below
assert(dataset.SOPClassUID == '1.2.840.10008.5.1.1.40')
assert(dataset.SOPInstanceUID == '1.2.840.10008.5.1.1.40.1')
# Return status, dataset
return 0x0000, dataset
ae.on_n_get = on_n_get
# Start listening for incoming association requests
ae.start_server(('', 11112))
