old_contents: from rest_framework import serializers
  
  from nodeconductor.quotas import models, utils
  from nodeconductor.core.serializers import GenericRelatedField
  
  
  class QuotaSerializer(serializers.HyperlinkedModelSerializer):
      scope = GenericRelatedField(related_models=utils.get_models_with_quotas(), read_only=True)
  
      class Meta(object):
          model = models.Quota
          fields = ('url', 'uuid', 'name', 'limit', 'usage', 'scope')
          read_only_fields = ('uuid', 'name')
          lookup_field = 'uuid'
  
      # TODO: cleanup after migration to drf 3
      def validate(self, attrs):
          from nodeconductor.structure.serializers import fix_non_nullable_attrs
          return fix_non_nullable_attrs(attrs)
  
new_contents: from rest_framework import serializers
  
  from nodeconductor.quotas import models, utils
  from nodeconductor.core.serializers import GenericRelatedField
  
  
  class QuotaSerializer(serializers.HyperlinkedModelSerializer):
      scope = GenericRelatedField(related_models=utils.get_models_with_quotas(), read_only=True)
  
      class Meta(object):
          model = models.Quota
          fields = ('url', 'uuid', 'name', 'limit', 'usage', 'scope')
          read_only_fields = ('uuid', 'name', 'scope', 'usage')
          lookup_field = 'uuid'
  
      # TODO: cleanup after migration to drf 3
      def validate(self, attrs):
          from nodeconductor.structure.serializers import fix_non_nullable_attrs
          return fix_non_nullable_attrs(attrs)
  
subject: Make quota usage read only (nc-263)