docs: def explicit_start_marker(self, source):
          """Does the python representation of this cell requires an explicit
          start of cell marker?"""
          if not self.use_cell_markers:
              return False
          if self.metadata:
              return True
          if self.cell_marker_start:
              start_code_re = re.compile('^' + self.comment + r'\s*' + self.cell_marker_start + r'\s*(.*)$')
              end_code_re = re.compile('^' + self.comment + r'\s*' + self.cell_marker_end + r'\s*$')
              if start_code_re.match(source[0]) or end_code_re.match(source[0]):
                  return False
  
          if all([line.startswith(self.comment) for line in self.source]):
              return True
          if LightScriptCellReader(self.fmt).read(source)[1] < len(source):
              return True
  
          return False