Add ProtectedFile, ProtectedImage, AdminFile and AdminImage.
from django.contrib import admin
from django.contrib.contenttypes.admin import GenericTabularInline
from .models import (Location, Permanence, Equipment, Lending, Position,
                    MembershipType, Membership, PublicFile, PublicImage,
                    ProtectedFile, ProtectedImage, AdminFile, AdminImage)

class AdminFileInline(GenericTabularInline):
    model = AdminFile

class AdminImageInline(GenericTabularInline):
    model = AdminImage

class ProtectedFileInline(GenericTabularInline):
    model = ProtectedFile

class ProtectedImageInline(GenericTabularInline):
    model = ProtectedImage

class PublicFileInline(GenericTabularInline):
    model = PublicFile

class PublicImageInline(GenericTabularInline):
    model = PublicImage

class MembershipInline(admin.StackedInline):
    model = Membership
    extra = 0

@admin.register(MembershipType)
class MembershipTypeAdmin(admin.ModelAdmin):

    class Media:
        js = ('tinymce/tinymce.min.js', 'js/tinymce_4_config.js')

@admin.register(Position)
class PositionAdmin(admin.ModelAdmin):
    class Media:
        js = ('tinymce/tinymce.min.js', 'js/tinymce_4_config.js')

admin.site.register(Location)
admin.site.register(Permanence)
admin.site.register(Equipment)
admin.site.register(Lending)
admin.site.register(PublicFile)
admin.site.register(PublicImage)
admin.site.register(ProtectedFile)
admin.site.register(ProtectedImage)
admin.site.register(AdminFile)
admin.site.register(AdminImage)

from django.contrib import admin
from django.contrib.contenttypes.admin import GenericTabularInline
from .models import (Location, Permanence, Equipment, Lending, Position,
                    MembershipType, Membership, PublicFile, PublicImage,
                    ProtectedFile, ProtectedImage, AdminFile, AdminImage)

class AdminFileInline(GenericTabularInline):
    model = AdminFile

class AdminImageInline(GenericTabularInline):
    model = AdminImage

class ProtectedFileInline(GenericTabularInline):
    model = ProtectedFile

class ProtectedImageInline(GenericTabularInline):
    model = ProtectedImage

class PublicFileInline(GenericTabularInline):
    model = PublicFile

class PublicImageInline(GenericTabularInline):
    model = PublicImage

class MembershipInline(admin.StackedInline):
    model = Membership
    extra = 0

@admin.register(MembershipType)
class MembershipTypeAdmin(admin.ModelAdmin):

    class Media:
        js = ('tinymce/tinymce.min.js', 'js/tinymce_4_config.js')

@admin.register(Position)
class PositionAdmin(admin.ModelAdmin):
    class Media:
        js = ('tinymce/tinymce.min.js', 'js/tinymce_4_config.js')

admin.site.register(Location)
admin.site.register(Permanence)
admin.site.register(Equipment)
admin.site.register(Lending)
admin.site.register(PublicFile)
admin.site.register(PublicImage)
