def get_raw_filename(raw,index=0):
        """ get filename from raw obj
        
        Parameters:
        -----------
        raw     : raw-obj to modify
        index   : index in list of filenames from raw.filenames <0>      
                  if index = list return filename list
        Returns:
        ----------
         first filename or None
        
        Example:
        ----------
         from jumeg.jumeg_base import jumeg_base as jb 
         fname = jb.get_raw_filename(raw)
        """
        if raw:
           if hasattr(raw,"filenames"): 
              if index == "list"                : return raw.filenames 
              if abs(index) < len(raw.filenames): return raw.filenames[index]
              return raw.filenames
           return raw.info.get('filename')
        return None