def METHOD_NAME(self, cell: NotebookNode) -> None:
    grade_id = cell.metadata.nbgrader['grade_id']
    try:
        source_cell = self.gradebook.find_source_cell(grade_id, self.notebook_id, self.assignment_id).to_dict()
        del source_cell['name']
        del source_cell['notebook']
        del source_cell['assignment']
    except MissingEntry:
        source_cell = {}
    source_cell.update({
        'cell_type': cell.cell_type,
        'locked': utils.is_locked(cell),
        'source': cell.source,
        'checksum': cell.metadata.nbgrader.get('checksum', None)
    })
    self.new_source_cells[grade_id] = source_cell