<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def attributes(self, resource_id=None):
 """Attribute endpoint for this resource with optional attribute id. This method will set the resource endpoint for working with Attributes. The HTTP GET method will return all attributes applied to this resource or if a resource id (attribute id) is provided it will return the provided attribute if exists on this resource. An attribute can be added to this resource using the HTTP POST method and passing a JSON body containing the attribute type and attribute value. Using the HTTP PUT method with a provided resource id an attribute can be updated. The HTTP DELETE method will remove the provided attribute from this resource. **Example Endpoints URI's** | HTTP Method | API Endpoint URI's | +==============+==============================================================+ | GET | /v2/groups/{resourceType}/{uniqueId}/attributes | | GET | /v2/groups/{resourceType}/{uniqueId}/attributes/{resourceId} | | DELETE | /v2/groups/{resourceType}/{uniqueId}/attributes/{resourceId} | | POST | /v2/groups/{resourceType}/{uniqueId}/attributes | | PUT | /v2/groups/{resourceType}/{uniqueId}/attributes/{resourceId} | Args: resource_id (Optional [string]):
 The resource id (attribute id). """

        resource = self.copy()
        resource._request_entity = 'attribute'
        resource._request_uri = '{}/attributes'.format(resource._request_uri)
        if resource_id is not None:
            resource._request_uri = '{}/{}'.format(resource._request_uri, resource_id)
        return resource