eliminated some hardcoded values

app/models/loan_charge.py

@@ -1,4 +1,6 @@
 from datetime import datetime, timezone, timedelta
+from os.path import devnull
+
 from app.extensions import db
 from sqlalchemy.orm import relationship
 
@@ -40,4 +42,8 @@ class LoanCharge(db.Model):
             'percent': self.percent,
             'description': self.description,
             'due': self.due
-        }
+        }
+
+    @classmethod
+    def get_loan_charge_by_debt_id(cls, debt_id):
+        return cls.query.filter_by(loan_id=debt_id)