code: def upgrade(nb, from_version=1):
      """Convert a notebook to the v2 format.
  
      Parameters
      ----------
      nb : NotebookNode
          The Python representation of the notebook to convert.
      from_version : int
          The version of the notebook to convert from.
      """
      if from_version == 1:
          newnb = new_notebook()
          ws = new_worksheet()
          for cell in nb.cells:
              if cell.cell_type == "code":
                  newcell = new_code_cell(
                      input=cell.get("code"),
                      prompt_number=cell.get("prompt_number"),
                  )
              elif cell.cell_type == "text":
                  newcell = new_text_cell(
                      "markdown", source=cell.get("text")
                  )
              ws.cells.append(newcell)
          newnb.worksheets.append(ws)
          return newnb
  
      raise ValueError(
          "Cannot convert a notebook from v%s to v2" % from_version
      )
  
imports: from __future__ import annotations
  from .nbbase import new_code_cell, new_notebook, new_text_cell, new_worksheet
label_desc: Use image node_id 1 for calling a global function with example usage: upgrade(nb, from_version) and returns: newnb