我有一个名为Coach的模型，我希望它可以在lesson_detail.html中访问，因为当我使用模板{{ coach.first_name }}时，什么都没有显示。我试图使用get_object_or_404从模型中提取数据，但我不确定需要在参数中放入什么。我尝试了一些东西，比如id=pk或下面的代码中的first_name=first_name，但我得到了一个错误，即变量未定义。
views.py

from django.shortcuts import render, get_object_or_404, reverse
from django.views import generic, View
from django.http import HttpResponseRedirect
from .models import Lesson, Coach, Feedback
from .forms import FeedbackForm
class LessonDetail(View):
    def get(self, request, slug, *args, **kwargs):
        queryset = Lesson.objects.filter(status=1)
        lesson = get_object_or_404(queryset, slug=slug)
        coach = get_object_or_404(Coach, first_name=first_name)
        feedbacks = lesson.feedbacks.filter(approved=True).order_by('-created_on')
        liked = False
        if lesson.likes.filter(id=self.request.user.id).exists():
            liked = True
        return render(
            request,
            "lesson_detail.html",
            {
                "lesson": lesson,
                "feedbacks": feedbacks,
                "coach": coach,
                "submitted_feedback": False,
                "liked": liked,
                "feedback_form": FeedbackForm(),
            },
        )

models.py

class Coach(models.Model):
    RECREATIONAL = 'recreational'
    FREESTYLE = 'freestyle'
    DANCE = 'dance'
    PAIRS = 'pairs'
    SPECIALIZATION_CHOICES = [
        (RECREATIONAL, 'Recreational'),
        (FREESTYLE, 'Freestyle'),
        (DANCE, 'Dance'),
        (PAIRS, 'Pairs'),
    ]
    first_name = models.CharField(max_length=80)
    last_name = models.CharField(max_length=80)
    email = models.EmailField(max_length=100)
    bio = models.CharField(max_length=140, help_text="Enter a brief bio")
    image = CloudinaryField('image', default='placeholder')
    specialization = models.CharField(max_length=20, choices=SPECIALIZATION_CHOICES, default=RECREATIONAL)
    years_of_experience = models.PositiveIntegerField(default='1', help_text="Enter a positive integer.")
    status = models.IntegerField(choices=STATUS, default=0)
    class Meta:
        ordering = ['pk']
    def __str__(self):
        return f'Coach {self.first_name} {self.last_name}'