Add stl() function

- `stl()` wraps R's "stl" function in Python
- STL is a decomposition method for time series

setup.cfg

@@ -89,6 +89,10 @@ extend-ignore =
     # Comply with black's style.
     # Source: https://github.com/psf/black/blob/master/docs/compatible_configs.md#flake8
     E203, W503, WPS348,
+    # Google's Python Style Guide is not reStructuredText
+    # until after being processed by Sphinx Napoleon.
+    # Source: https://github.com/peterjc/flake8-rst-docstrings/issues/17
+    RST201,RST203,RST301,
     # String constant over-use is checked visually by the programmer.
     WPS226,
     # Allow underscores in numbers.
@@ -103,6 +107,9 @@ extend-ignore =
     WPS429,
 
 per-file-ignores =
+    # Top-levels of a sub-packages are intended to import a lot.
+    **/__init__.py:
+        F401,WPS201,
     docs/conf.py:
         # Allow shadowing built-ins and reading __*__ variables.
         WPS125,WPS609,
@@ -132,15 +139,9 @@ per-file-ignores =
         WPS115,
         # Numbers are normal in config files.
         WPS432,
-    src/urban_meal_delivery/db/__init__.py:
-        # Top-level of a sub-packages is intended to import a lot.
-        F401,WPS201,
-    src/urban_meal_delivery/db/utils/__init__.py:
-        # Top-level of a sub-packages is intended to import a lot.
-        F401,
-    src/urban_meal_delivery/forecasts/__init__.py:
-        # Top-level of a sub-packages is intended to import a lot.
-        F401,
+    src/urban_meal_delivery/forecasts/decomposition.py:
+        # The module does not have a high cognitive complexity.
+        WPS232,
     src/urban_meal_delivery/forecasts/timify.py:
         # No SQL injection as the inputs come from a safe source.
         S608,
@@ -169,9 +170,6 @@ per-file-ignores =
         WPS432,
         # When testing, it is normal to use implementation details.
         WPS437,
-    tests/db/fake_data/__init__.py:
-        # Top-level of a sub-packages is intended to import a lot.
-        F401,WPS201,
 
 # Explicitly set mccabe's maximum complexity to 10 as recommended by
 # Thomas McCabe, the inventor of the McCabe complexity, and the NIST.