Unexpected during evaluation

[brynrhodes]

Given the following library:

library Queries

using QICore version '4.1.1'

include FHIRHelpers version '4.1.000'

parameter "Measurement Period" Interval<DateTime> default Interval[@2023-01-01T00:00:00.0Z, @2023-12-31T23:59:59.999Z]

context Patient

define "Blood Pressure Observations":
  ["Observation Blood Pressure Profile"]

define "Encounters With Blood Pressure":
  [Encounter] E
    with ["Observation Blood Pressure Profile"] O
      such that O.effective during E.period

define "Encounter-1 Period":
  singleton from (
    [Encounter] E
        where E.id = 'Encounter-1'
        return E.period
  )

define "Observation Blood Pressure Effective":
  singleton from (
    ["Observation Blood Pressure Profile"] O
      return O.effective
  )

define "Is During":
  "Observation Blood Pressure Effective" during "Encounter-1 Period"

define "On Or After Start Of":
  "Observation Blood Pressure Effective" on or after start "Encounter-1 Period"

define "On Or Before End Of":
  "Observation Blood Pressure Effective" on or before end "Encounter-1 Period"

And the following Encounter and Observation resources:

{
    "resourceType": "Encounter",
    "id": "Encounter-1",
    "meta": {
        "profile": [
          "http://hl7.org/fhir/us/qicore/StructureDefinition/qicore-encounter"
        ]
    },
    "subject": {
      "reference": "Patient/example"
    },
    "status": "finished",
    "class": {
      "code": "AMB",
      "system": "http://terminology.hl7.org/CodeSystem/v3-ActCode",
      "display": "ambulatory"
    },
    "type": [
      {
        "coding": [
          {
            "code": "3391000175108",
            "system": "http://snomed.info/sct",
            "display": "Office visit for pediatric care and assessment (procedure)"
          }
        ]
      }
    ],
    "period": {
      "start": "2023-01-10T10:00:00.000Z",
      "end": "2023-01-10T11:00:00.000Z"
    }
  }

{
  "resourceType": "Observation",
  "id": "blood-pressure",
  "meta": {
    "profile": [
      "http://hl7.org/fhir/StructureDefinition/bp"
    ]
  },
  "text": {
    "status": "generated",
    "div": "<div xmlns=\"http://www.w3.org/1999/xhtml\"><p><b>Generated Narrative with Details</b></p><p><b>id</b>: blood-pressure</p><p><b>meta</b>: </p><p><b>status</b>: final</p><p><b>category</b>: Vital Signs <span style=\"background: LightGoldenRodYellow\">(Details : {http://terminology.hl7.org/CodeSystem/observation-category code 'vital-signs' = 'Vital Signs', given as 'Vital Signs'})</span></p><p><b>code</b>: Blood pressure systolic and diastolic <span style=\"background: LightGoldenRodYellow\">(Details : {LOINC code '85354-9' = 'Blood pressure panel with all children optional', given as 'Blood pressure panel with all children optional'})</span></p><p><b>subject</b>: <a href=\"Patient-example.html\">Amy Shaw. Generated Summary: id: example; Medical Record Number = 1032702 (USUAL); active; Amy V. Shaw ; ph: 555-555-5555(HOME), amy.shaw@example.com; gender: female; birthDate: 2007-02-20</a></p><p><b>encounter</b>: GP Visit</p><p><b>effective</b>: 02/07/1999 12:00:00 AM</p><blockquote><p><b>component</b></p><p><b>code</b>: Systolic blood pressure <span style=\"background: LightGoldenRodYellow\">(Details : {LOINC code '8480-6' = 'Systolic blood pressure', given as 'Systolic blood pressure'})</span></p><p><b>value</b>: 109 mmHg<span style=\"background: LightGoldenRodYellow\"> (Details: UCUM code mm[Hg] = 'mm[Hg]')</span></p></blockquote><blockquote><p><b>component</b></p><p><b>code</b>: Diastolic blood pressure <span style=\"background: LightGoldenRodYellow\">(Details : {LOINC code '8462-4' = 'Diastolic blood pressure', given as 'Diastolic blood pressure'})</span></p><p><b>value</b>: 44 mmHg<span style=\"background: LightGoldenRodYellow\"> (Details: UCUM code mm[Hg] = 'mm[Hg]')</span></p></blockquote></div>"
  },
  "status": "final",
  "category": [
    {
      "coding": [
        {
          "system": "http://terminology.hl7.org/CodeSystem/observation-category",
          "code": "vital-signs",
          "display": "Vital Signs"
        }
      ],
      "text": "Vital Signs"
    }
  ],
  "code": {
    "coding": [
      {
        "system": "http://loinc.org",
        "code": "85354-9",
        "display": "Blood pressure panel with all children optional"
      }
    ],
    "text": "Blood pressure systolic and diastolic"
  },
  "subject": {
    "reference": "Patient/example",
    "display": "Amy Shaw"
  },
  "encounter": {
    "display": "GP Visit"
  },
  "effectiveDateTime": "2023-01-10T10:10Z",
  "component": [
    {
      "code": {
        "coding": [
          {
            "system": "http://loinc.org",
            "code": "8480-6",
            "display": "Systolic blood pressure"
          }
        ],
        "text": "Systolic blood pressure"
      },
      "valueQuantity": {
        "value": 109,
        "unit": "mmHg",
        "system": "http://unitsofmeasure.org",
        "code": "mm[Hg]"
      }
    },
    {
      "code": {
        "coding": [
          {
            "system": "http://loinc.org",
            "code": "8462-4",
            "display": "Diastolic blood pressure"
          }
        ],
        "text": "Diastolic blood pressure"
      },
      "valueQuantity": {
        "value": 44,
        "unit": "mmHg",
        "system": "http://unitsofmeasure.org",
        "code": "mm[Hg]"
      }
    }
  ]
}

The result of the "Is During" expression should be true, but is returning null