Added the is_nominal pseudo property to the Account data model.

src/accounting/models.py

@@ -198,6 +198,14 @@ class Account(db.Model):
                 return
         self.l10n.append(AccountL10n(locale=current_locale, title=value))
 
+    @property
+    def is_nominal(self) -> bool:
+        """Returns whether the account is a nominal account.
+
+        :return: True if the account is a nominal account, or False otherwise.
+        """
+        return self.base_code[0] not in {"1", "2", "3"}
+
     @property
     def query_values(self) -> list[str]:
         """Returns the values to be queried.