code: def double_percent_options_to_metadata(options):
      
      matches = _PERCENT_CELL.findall('# %%' + options)
  
      # Fail safe when regexp matching fails #116
      # (occurs e.g. if square brackets are found in the title)
      if not matches:
          return {'title': options.strip()}
  
      matches = matches[0]
  
      # Fifth match are JSON metadata
      if matches[4]:
          metadata = json_options_to_metadata(matches[4], add_brackets=False)
      else:
          metadata = {}
  
      # Third match is cell type
      cell_type = matches[2]
      if cell_type:
          metadata['cell_type'] = cell_type[1:-1]
  
      # Second and fourth match are description
      title = [matches[i].strip() for i in [1, 3]]
      title = [part for part in title if part]
      if title:
          title = ' '.join(title)
          cell_depth = 0
          while title.startswith('%'):
              cell_depth += 1
              title = title[1:]
  
          if cell_depth:
              metadata['cell_depth'] = cell_depth
          metadata['title'] = title.strip()
  
      return metadata
docs: Parse double percent options