无法移动 URL 以在 Django 中导入 URL

Django 2.2.5

直到现在，我在移动 url 时都没有遇到问题。

报告/reporting.html（索引）：

...
{% url "line_chart_json" %}
...

报告/views.py

class LineChartJSONView(BaseLineChartView):
    def get_labels(self):
        """Return 7 labels for the x-axis."""
        return ["January", "February", "March", "April", "May", "June", "July"]
    ....

当它在主应用程序 url.py 中时，就可以了

from django.urls import path, include
from reporting.views import LineChartJSONView
urlpatterns = [
    ...
    path('reporting/', include('reporting.urls')),
    path('line_chart/json/', LineChartJSONView.as_view(),
          name='line_chart_json'),
]

当我将其移至报告时

from django.urls import path
from . import views
from .views import LineChartJSONView

app_name = 'reporting'
urlpatterns = [
    path('', views.summary_properties_user,
         name='index'),
    path('line_chart/json/', LineChartJSONView.as_view(),
         name='line_chart_json'),
]

我在reporting.html上使用它返回一个错误：

NoReverseMatch at /reporting/
Reverse for 'line_chart_json' not found. 'line_chart_json' is not a valid view function or pattern name.

我假设一个简单的疏忽。仅仅几周之后，Django URLs 仍然让我摸不着头脑。