Fix formula node (catagory as well as make every input optional)

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "basic_data_handling"
-version = "0.4.4"
+version = "0.4.5"
 description = """Basic Python functions for manipulating data that every programmer is used to, lightweight with no additional dependencies.
 
 Supported data types:

src/basic_data_handling/math_formula_node.py

@@ -43,14 +43,16 @@ class MathFormula(ComfyNodeABC):
     @classmethod
     def INPUT_TYPES(cls):
         return {
-            "required": ContainsDynamicDict({
-                "formula": (IO.STRING, {"default": "-e() ** -2"}),
-                "a": (IO.NUMBER, {"default": 3.0, "_dynamic": "letter"}),
+            "required": {
+                "formula": (IO.STRING, {"default": "-pi() ** 2"}),
+            },
+            "optional": ContainsDynamicDict({
+                "a": (IO.NUMBER, {"default": 0.0, "_dynamic": "letter"}),
             }),
         }
 
     RETURN_TYPES = (IO.FLOAT,)
-    CATEGORY = "math"
+    CATEGORY = "Basic/maths"
     DESCRIPTION = cleandoc(__doc__ or "")
     FUNCTION = "evaluate"