From b610397433d4df41b35a4e867e65e6b92e51c1aa Mon Sep 17 00:00:00 2001
From: Wenjie Du <wenjay.du@gmail.com>
Date: Sun, 14 Apr 2024 17:45:48 +0800
Subject: [PATCH] refactor: remove locf.modules and add assertions in
 bttf.core;

---
 pypots/forecasting/bttf/core.py              | 5 +++++
 pypots/imputation/locf/{modules => }/core.py | 0
 pypots/imputation/locf/model.py              | 5 +++--
 pypots/imputation/locf/modules/__init__.py   | 6 ------
 4 files changed, 8 insertions(+), 8 deletions(-)
 rename pypots/imputation/locf/{modules => }/core.py (100%)
 delete mode 100644 pypots/imputation/locf/modules/__init__.py

diff --git a/pypots/forecasting/bttf/core.py b/pypots/forecasting/bttf/core.py
index fb232e2e..ffd8ef67 100644
--- a/pypots/forecasting/bttf/core.py
+++ b/pypots/forecasting/bttf/core.py
@@ -218,6 +218,11 @@ def BTTF_forecast(
 ):
     dim1, dim2, T = dense_tensor.shape
     start_time = T - pred_step
+    assert start_time > -1, (
+        "start_time should be larger than -1, "
+        "namely the number of the input tensor's time steps should be larger than pred_step."
+    )
+    assert start_time >= np.max(time_lags), "start_time should be >= max(time_lags)"
     max_count = int(np.ceil(pred_step / multi_step))
     tensor_hat = np.zeros((dim1, dim2, max_count * multi_step))
 
diff --git a/pypots/imputation/locf/modules/core.py b/pypots/imputation/locf/core.py
similarity index 100%
rename from pypots/imputation/locf/modules/core.py
rename to pypots/imputation/locf/core.py
diff --git a/pypots/imputation/locf/model.py b/pypots/imputation/locf/model.py
index f634f87f..e7c47366 100644
--- a/pypots/imputation/locf/model.py
+++ b/pypots/imputation/locf/model.py
@@ -13,14 +13,15 @@
 import numpy as np
 import torch
 
-from .modules.core import locf_numpy, locf_torch
+from .core import locf_numpy, locf_torch
 from ..base import BaseImputer
 from ...utils.logging import logger
 
 
 class LOCF(BaseImputer):
     """LOCF (Last Observed Carried Forward) imputation method. A naive imputation method that fills missing values
-    with the last observed value. Simple but commonly used in practice.
+    with the last observed value. When time-series data gets inverse on the time dimension, this method can also be
+    seen as NOCB (Next Observation Carried Backward). Simple but commonly used in practice.
 
     Parameters
     ----------
diff --git a/pypots/imputation/locf/modules/__init__.py b/pypots/imputation/locf/modules/__init__.py
deleted file mode 100644
index ceaa7ee3..00000000
--- a/pypots/imputation/locf/modules/__init__.py
+++ /dev/null
@@ -1,6 +0,0 @@
-"""
-
-"""
-
-# Created by Wenjie Du <wenjay.du@gmail.com>
-# License: BSD-3-Clause