trasaction.py

from django.db import models
from bee.models import ModelMixin
from .extract import Extract


class Transaction(ModelMixin):
    paying = models.OneToOneField(
        Extract,
        on_delete=models.CASCADE,
        related_name='paying',
        verbose_name='extrato pagamento'
    )
    receiver = models.OneToOneField(
        Extract,
        on_delete=models.CASCADE,
        related_name='receiver',
        verbose_name='extrato recebimento'
    )
    proof = models.CharField(
        max_length=19,
        unique=True,
        verbose_name='comprovante'
    )
    amount = models.DecimalField(
        max_digits=18,
        decimal_places=8,
        verbose_name='valor'
    )
    fee = models.DecimalField(
        max_digits=18,
        decimal_places=8,
        verbose_name='taxa'
    )

    class Meta():
        verbose_name = "Transação"
        verbose_name_plural = 'Transações'

    def invoice():
        return self.invoice

-----------------------------------------------------------------

payment.py

from django.db import models
from bee.models import ModelMixin
from .invoice import Invoice
from wallet.models import Transaction


class Payment(ModelMixin):
    invoice = models.ForeignKey(
        Invoice,
        on_delete=models.CASCADE,
        verbose_name='fatura'
    )
    transaction = models.OneToOneField(
        Transaction,
        on_delete=models.CASCADE,
        related_name='transaction',
        verbose_name='transação'
    )

    class Meta:
        verbose_name = "Pagamento"
        verbose_name_plural = 'Pagamentos'

    def __str__(self):
        return f'''
            {self.transaction.payment.user.username.lower()} > {self.transaction.receipt.user.username.lower()} |
            {self.transaction.payment.coin.code.upper()} {self.transaction.amount} | {self.transaction.proof}
        '''