Issue adding Markers

[ron-eyal]

I've seen examples with this same code, but when I try to run it, it gives me an error.

I'm trying to add a marker to an AAF using this code:

with aaf2.open(destination, 'rw') as destination_aaf:
            destination_mob_toplevel = next(destination_aaf.content.toplevel(), None)
            ems = destination_aaf.create.EventMobSlot()
            ems['EditRate'].value = '24000/1001'
            ems['SlotID'].value = 1000
            ems['PhysicalTrackNumber'].value = 10
            sequence = destination_aaf.create.Sequence("DescriptiveMetadata") #  This is the line causing the error
            marker = destination_aaf.create.DescriptiveMarker()
            marker.media_kind = "DescriptiveMetadata"
            described_slots = set([1])
            marker['DescribedSlots'].value = described_slots
            marker['Position'].value = 100
            marker['Comment'].value = "This is a comment"
            marker['CommentMarkerUser'].value = "User Name"
            sequence.components.append(marker)
            ems.segment = sequence
            destination_mob_toplevel.slots.append(ems)

I get the following error:

line 183, in add_markers
    sequence = destination_aaf.create.Sequence("DescriptiveMetadata")
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/file.py", line 63, in create_instance
    return self.from_name(self.class_name, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/file.py", line 54, in from_name
    obj.__init__(*args, **kwargs)
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/components.py", line 75, in __init__
    super(Sequence, self).__init__(media_kind, length)
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/components.py", line 21, in __init__
    self.media_kind = media_kind or 'picture'
    ^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/components.py", line 48, in media_kind
    self.datadef = self.root.dictionary.lookup_datadef(value)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/dictionary.py", line 239, in lookup_datadef
    return lookup_def(self, name, DataDef, 'DataDefinitions')
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/dictionary.py", line 37, in lookup_def
    raise Exception("No Definition: %s" % str(name))
Exception: No Definition: descriptivemetadata

Oddly, if I change the line from "DescriptiveMetadata" to "Descriptive metadata" with a space like this:
sequence = destination_aaf.create.Sequence("Descriptive metadata")

it gets past that line but has an error on the next line:

in edit_aaf_main
    marker = destination_aaf.create.DescriptiveMarker()
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/file.py", line 63, in create_instance
    return self.from_name(self.class_name, *args, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/file.py", line 54, in from_name
    obj.__init__(*args, **kwargs)
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/components.py", line 339, in __init__
    super(Event, self).__init__(media_kind='DescriptiveMetadata')
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/components.py", line 21, in __init__
    self.media_kind = media_kind or 'picture'
    ^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/components.py", line 48, in media_kind
    self.datadef = self.root.dictionary.lookup_datadef(value)
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/dictionary.py", line 239, in lookup_datadef
    return lookup_def(self, name, DataDef, 'DataDefinitions')
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/X/.local/share/virtualenvs/X/lib/python3.11/site-packages/aaf2/dictionary.py", line 37, in lookup_def
    raise Exception("No Definition: %s" % str(name))
Exception: No Definition: descriptivemetadata

[ron-eyal]

I think I figured out the cause of the issue. The destination_aaf that I was modifying had a dictionary with some differences to an empty AAF created using pyaaf2. Since there was no definition of "descriptivemetadata" in that dictionary, an error was happening on those lines. That dictionary did have a definition of "Descriptive Metadata" with a space, so it got through that first step with that change, but then would fail on creating the marker, which again is expecting "descriptivemetadata" in the dictionary.

Is there a way to add new entries to an AAF's dictionary to resolve this issue?