fix: use postponed evaluation (#124)

* 6899ae1 switched list[... to List[... for compat with python 3.8
* instead, opt into postponed evaluation per suggestion
* use CI matrix to test python 3.8 - 3.11

.github/workflows/ex-workflow.yml

@@ -39,7 +39,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: 3.9
+          python-version: 3.8
 
       - name: Print python version
         run: |
@@ -89,6 +89,8 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       fail-fast: false
+      matrix:
+        python: [3.8, 3.9, "3.10", "3.11"]
     env:
       script-directory: scripts
       etc-directory: etc
@@ -118,7 +120,7 @@ jobs:
       - name: Setup Python
         uses: actions/setup-python@v4
         with:
-          python-version: 3.9
+          python-version: ${{ matrix.python }}
 
       - name: Install Python packages
         run: |
@@ -147,11 +149,13 @@ jobs:
         working-directory: ${{env.etc-directory}}
 
       - name: Run processing script
+        if: matrix.python == '3.9'
         run: |
           python process-scripts.py
         working-directory: ${{env.script-directory}}
 
       - name: Build mf6examples LaTeX document
+        if: matrix.python == '3.9'
         shell: python
         run: |
           import sys
@@ -182,12 +186,14 @@ jobs:
                       print(stderr)
 
       - name: Rename and move the LaTeX document
+        if: matrix.python == '3.9'
         run: |
           ls -l ./doc/
           mv ./doc/mf6examples.pdf mf6examples.pdf
           ls -l ./
 
       - name: Upload build artifacts for current release
+        if: matrix.python == '3.9'
         uses: actions/upload-artifact@v3
         with:
           name: current

common/DisvGridMerger.py

@@ -1,3 +1,5 @@
+from __future__ import annotations
+
 from math import sqrt
 import copy
 

common/DisvPropertyContainer.py

@@ -1,6 +1,7 @@
+from __future__ import annotations
+
 import copy
 from itertools import cycle
-from typing import List
 
 import matplotlib.pyplot as plt
 import numpy as np
@@ -104,10 +105,10 @@ class DisvPropertyContainer:
     nlay: int
     ncpl: int
     nvert: int
-    vertices: List[list]  # [[iv, xv, yv], ...]
-    cell2d: List[list]  # [[ic, xc, yc, ncvert, icvert], ...]
+    vertices: list[list]  # [[iv, xv, yv], ...]
+    cell2d: list[list]  # [[ic, xc, yc, ncvert, icvert], ...]
     top: np.ndarray
-    botm: List[np.ndarray]
+    botm: list[np.ndarray]
     origin_x: float
     origin_y: float
     rotation: float
@@ -541,7 +542,7 @@ def plot_grid(
             plot_time = -1.0
 
         if not isinstance(grid_color, tuple):
-            grid_color = (grid_color, )
+            grid_color = (grid_color,)
 
         ColorCycler = grid_color
         if plot_time > 0.0 and grid_color == ("grey",):