String identifying the type of cell.
The code cell's prompt number. Will be null if the cell has not been run.
Optional idA string field representing the identifier of this particular cell.
Notebook format 4.4 requires no id field, but format 4.5 requires an id field. We need to handle both cases, so we make id optional here.
Cell-level metadata.
Execution, display, or stream outputs.
Contents of the cell, represented as an array of lines.
A code cell.