Add mypy pre-commit hook

.mypy.ini

@@ -1,4 +1,5 @@
 [mypy]
+# equivalent to "files" in .pre-commit-config.yaml
 files = Bio,BioSQL
 show_error_context = true
 show_column_numbers = true

.pre-commit-config.yaml

@@ -31,6 +31,12 @@ repos:
             'flake8-rst-docstrings>=0.2.3',
             'pydocstyle>=6.0.0',
         ]
+-   repo: https://github.com/pre-commit/mirrors-mypy
+    rev: v1.4.1
+    hooks:
+    -   id: mypy
+        # equivalent to "files" in .mypy.ini
+        files: '^(Bio|BioSQL)/'
 -   repo: https://github.com/asottile/blacken-docs
     rev: 1.14.0
     hooks:

ci-dependencies.txt

@@ -29,3 +29,6 @@ numpydoc==1.3.1
 pygments
 sphinx==4.3.2
 sphinx_rtd_theme
+
+# Static type checking
+mypy