code: def mk_fmtfld(nt_item, joinchr=" ", eol="\n"):
      
      fldstrs = []
      # Default formats based on fieldname
      fld2fmt = {
          'hdrgo' : lambda f: "{{{FLD}:1,}}".format(FLD=f),
          'dcnt' : lambda f: "{{{FLD}:6,}}".format(FLD=f),
          'level' : lambda f: "L{{{FLD}:02,}}".format(FLD=f),
          'depth' : lambda f: "D{{{FLD}:02,}}".format(FLD=f),
      }
      for fld in nt_item._fields:
          if fld in fld2fmt:
              val = fld2fmt[fld](fld)
          else:
              val = "{{{FLD}}}".format(FLD=fld)
          fldstrs.append(val)
      return "{LINE}{EOL}".format(LINE=joinchr.join(fldstrs), EOL=eol)
docs: Given a namedtuple, return a format_field string.