I have the following models:

class Position(BaseModel):
    name = models.CharField()

class Metric(BaseModel):
    name = models.CharField()

class PositionKPI(BaseModel):
    position = models.ForeignKey(Position)
    metric = models.ForeignKey(Metric)
    expectation = models.FloatField()

class Employee(BaseModel):
    position = models.ForeignKey(Position)

class EmployeeKPI(BaseModel):
    employee = models.ForeignKey(Employee)
    metric = models.ForeignKey(Metric)
    value = models.FloatField()

    def kpi(self):
        return PositionKPI.objects.filter(position=self.employee.position, metric=self.metric).first()

I believe it’s possible to rewrite the kpi method as a relation.
In SQL it would look something like this:

select
  positionkpi.* 
from employeekpi 
  join employee on employee.id = employeekpi.employee_id
  join positionkpi on positionkpi.id = employee.position_id
      and positionkpi.metric_id = employeekpi.metric_id

Please advise how to do it