docs: def get_metatab_doc(nb_path):
      """Read a notebook and extract the metatab document. Only returns the first document"""
  
      from metatab.generate import CsvDataRowGenerator
      from metatab.rowgenerators import TextRowGenerator
      from metatab import MetatabDoc
  
      with open(nb_path) as f:
          nb = nbformat.reads(f.read(), as_version=4)
  
      for cell in nb.cells:
          source = ''.join(cell['source']).strip()
          if source.startswith('%%metatab'):
              return MetatabDoc(TextRowGenerator(source))