Query: What was my body weight during the last observation?, FHIR Resource: {'resourceType': 'Observation', 'status': 'final', 'category': [{'coding': [{'system': 'http://terminology.hl7.org/CodeSystem/observation-category', 'code': 'vital-signs', 'display': 'Vital signs'}]}], 'code': {'coding': [{'system': 'http://loinc.org', 'code': '59576-9', 'display': 'Body mass index (BMI) [Percentile] Per age and sex'}], 'text': 'Body mass index (BMI) [Percentile] Per age and sex'}, 'subject': {'reference': 'urn:uuid:b927e156-a549-ae83-eb4b-da93419baf51'}, 'effectiveDateTime': '2014-09-26T01:50:50+05:30', 'valueQuantity': {'value': 63.586, 'unit': '%', 'system': 'http://unitsofmeasure.org', 'code': '%'}, 'interpretation': None}