relationship getters between models

app/models.py

@@ -1,5 +1,5 @@
 from app import db
-from sqlalchemy import Column, INTEGER, String
+from sqlalchemy import Column, INTEGER, String, select
 
 class Vendor(db.Model):
     __tablename__ = 'vendor'
@@ -7,11 +7,27 @@ class Vendor(db.Model):
     name          = Column('name', String(), nullable=False)
     bc_id         = Column('bc_id', INTEGER(), nullable=True)
 
+    def get_budget_category(self):
+        return db.session.execute(select(BudgetCategory).where(BudgetCategory.id==self.bc_id)).first()
+    
+    def get_line_items(self):
+        return db.session.execute(select(LineItem).where(LineItem.vendor_id==self.id)).all()
+
 class BudgetCategory(db.Model):
     __tablename__ = 'budget_category'
     id            = Column('id', INTEGER(), primary_key=True, autoincrement=True)
     name          = Column('name', String(), nullable=False)
 
+    def get_vendors(self):
+        return db.session.execute(select(Vendor).where(Vendor.bc_id==self.id)).all()
+
+    def get_line_items(self):
+        line_items = []
+        vendors = self.get_vendors()
+        for vendor in vendors:
+            line_items += vendor.get_line_items()
+        return line_items
+    
 class LineItem(db.Model):
     __tablename__       = 'line_item'
     id                  = Column('id', INTEGER(), primary_key=True, autoincrement=True)
@@ -23,3 +39,11 @@ class LineItem(db.Model):
     confirmation_code   = Column('confirmation_code', INTEGER(), nullable=True)
     note                = Column('note', String(), nullable=True)
 
+    def get_parent_line(self):
+        return db.session.execute(select(LineItem).where(LineItem.id==self.parent_line_item_id)).first()
+    
+    def get_children_lines(self):
+        return db.session.execute(select(LineItem).where(LineItem.parent_line_item_id==self.id)).all()
+
+    def get_vendor(self):
+        return db.session.execute(select(Vendor).where(Vendor.id==self.vendor_id)).first()