<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def subjects_list(self, api_url=None, offset=0, limit=-1, properties=None):
 """Get list of subject resources from a SCO-API. Parameters api_url : string, optional Base Url of the SCO-API. Uses default API if argument not present. offset : int, optional Starting offset for returned list items limit : int, optional Limit the number of items in the result properties : List(string) List of additional object properties to be included for items in the result Returns ------- List(scoserv.ResourceHandle) List of resource handles (one per subject in the listing) """

        # Get subject listing Url for given SCO-API and return the retrieved
        # resource listing
        return sco.get_resource_listing(
            self.get_api_references(api_url)[sco.REF_SUBJECTS_LIST],
            offset,
            limit,
            properties
        )