Add get_symbol for functions in Python API

- This allows for easier pattern restrictions on function wildcards

src/api/python.rs

@@ -3060,6 +3060,11 @@ impl PythonFunction {
         self.id.is_symmetric()
     }
 
+    /// Get the symbol of the function.
+    pub fn get_symbol(&self) -> PythonExpression {
+        Atom::new_var(self.id).into()
+    }
+
     /// Create a Symbolica expression or transformer by calling the function with appropriate arguments.
     ///
     /// Examples

symbolica.pyi

@@ -941,6 +941,9 @@ class Function:
     def is_symmetric(self) -> bool:
         """Returns `True` iff this function is symmetric."""
 
+    def get_symbol(self) -> Expression:
+        """Get the symbol of the function."""
+
     @overload
     def __call__(self, *args: Expression | int) -> Expression:
         """