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ID not found in layout for dcc.Upload() example but callback works. Why is this so?

I am using dcc.Upload

dcc.Upload(
                id='upload-data',
                children=html.Div([
                    "Drag and Drop or ",
                    html.A('Select Fasta Files')
                ]),
                style={
                    'width': '100%',
                    'height': '60px',
                    'lineHeight':'60px',
                    'borderWidth': '1px',
                    'borderStyle': 'dashed',
                    'borderRadius': '5px',
                    'testAlign': 'center',
                    'margin': '10px'
                },
                multiple=True
                ),

It is a carbon copy of the first example in the documentation.
I use the example callback almost as it is to read in and output protein sequence files with a .fasta suffix.

def register_entrez_callbacks(app):
    # callbacks for entrez_page
    # callbacks for processing file uploadprocessing file upload
    @app.callback(Output('output-data-upload', 'children'),
                  [Input('upload-data', 'contents')],
                  [State('upload-data', 'filename'),
                   State('upload-data', 'last_modified')])
    def process_upload(list_of_contents, list_of_names, list_of_dates):
        print(f"listContents: {type(list_of_contents)}\n{list_of_contents[0]}")
        print(f"listFilename: {type(list_of_names)}\n{list_of_names[0]}")
        print(f"listModified: {type(list_of_dates)}\n{list_of_dates[0]}")
        if list_of_contents is not None:
            children=[
                parse_contents(c,n,d) for c,n,d in
                zip(list_of_contents, list_of_names, list_of_dates)
            ]
            return children

    # helpers for functions
    # for uplaod
    def parse_contents(contents, filename, date):
        content_type, content_string, = contents.split(',')
        print(f'name:{type(filename)}\n{filename}\n')
        print(f'type:{type(content_type)}\n{content_type}\n')
        print(f'string:{type(content_string)}\n{content_string}\n')
        decoded = base64.b64decode(content_string)
        print(f'decoded:{decoded}\n')
        #seq1 = SeqIO.read(decoded, "fasta")
        seq_str = str(decoded)
        print(f'seq_str: {seq_str}')
        '''
        try:
            
            seq = SeqIO.read(decoded, "fasta")
            print(f'\n\nseq:{seq}')
        except Exception as e:
            print(e)
            return html.Div([
                'Error processing file upload'
            ])
        '''
        return html.Div([
            html.H5(filename),
            html.H6(datetime.datetime.fromtimestamp(date)),

            html.Div(
                f'{seq_str}'
            ),
            html.Hr(),

            #debugging content
            html.Div('Raw Content'),
            html.Pre(contents[0:100] + '...', style={
                'whiteSpace': 'pre-wrap',
                'wordBreak': 'break-all'
            })

        ])

My layout also has:

html.Div(#show the uploaded file contents as string
                id="output-data-upload"
            ),

I can see it in the browser, inspect it and it’s there.

along the right column that is the result, I can see the contents of the fasta file and the raw content.
But the errors that I hid for that screenshot:

Is this a bug and if so is it safe to just ignore it?