docs: @Override
  	public Response deleteFile(String CorpNum, int ItemCode, String MgtKey,
  			String FileID, String UserID) throws PopbillException {
  		if (MgtKey == null || MgtKey.isEmpty())
  			throw new PopbillException(-99999999, "관리번호가 입력되지 않았습니다.");
  		if (FileID == null || FileID.isEmpty())
  			throw new PopbillException(-99999999, "파일아이디가 입력되지 않았습니다.");
  		
  		return httppost("/Statement/" + ItemCode + "/" + MgtKey + "/Files/" + FileID,
  				CorpNum, null, UserID, "DELETE", Response.class);
  		
  	}