how to use reverse query data from a child model to do arithmetic's in parent model?

[Vansh Jagyasi -IIITK]

I have created a model location, and a model transaction which has a many 
to one relation with location which has the information of a transaction 
done at a particular location, say 3 dollars spent at macdonalds, now I 
want to find all the transactions related to a particular location and add 
the amount to find the total amount spent,please help

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from django.db import models


class location(models.Model):
    name=models.CharField(max_length=100)
    total_amount_spent=models.FloatField(default=0)
    def __str__(self):
        return self.name
    
class transaction(models.Model):
    location_name=models.ForeignKey(location,on_delete=models.CASCADE,null=True)
    date_time=models.DateTimeField(null=True)
    amount=models.FloatField(null=True)
    def __int__(self):
        return self.id