Query: What was my potassium level during my last lab test?, FHIR Resource: {'resourceType': 'Observation', 'status': 'final', 'category': [{'coding': [{'system': 'http://terminology.hl7.org/CodeSystem/observation-category', 'code': 'laboratory', 'display': 'Laboratory'}]}], 'code': {'coding': [{'system': 'http://loinc.org', 'code': '2085-9', 'display': 'Cholesterol in HDL [Mass/volume] in Serum or Plasma'}], 'text': 'Cholesterol in HDL [Mass/volume] in Serum or Plasma'}, 'subject': {'reference': 'urn:uuid:c0fdafe6-f9ca-2319-717c-11489d1189b8'}, 'effectiveDateTime': '2014-10-31T09:41:41+05:30', 'valueQuantity': {'value': 66.63, 'unit': 'mg/dL', 'system': 'http://unitsofmeasure.org', 'code': 'mg/dL'}, 'interpretation': None}