code: def format_sparql(item, dt_format='turtle', **kwargs):
      
      try:
          rtn_val = json.dumps(item.value)
          rtn_val = item.value
      except:
          if 'time' in item.class_type.lower() \
                  or 'date' in item.class_type.lower():
              rtn_val = item.value.isoformat()
          else:
              rtn_val = str(item.value)
      if hasattr(item, "datatype"):
          if hasattr(item, "lang") and item.lang:
              rtn_val = '%s@%s' % (json.dumps(rtn_val), item.lang)
          else:
              dt = item.datatype
              if dt_format == "uri":
                  dt = item.datatype.sparql_uri
              if item.datatype in ["xsd_string",
                                   "xsd_dateTime",
                                   "xsd_time",
                                   "xsd_date"]:
                  rtn_val = json.dumps(rtn_val)
              else:
                  rtn_val = '"%s"' % json.dumps(rtn_val)
              rtn_val = '%s^^%s' % (rtn_val, dt.sparql)
      return rtn_val
docs: Formats a datatype value to a SPARQL representation
  
      args:
          item: the datatype object
          dt_format: the return format ['turtle', 'uri']