Search parameter for contraint example

{
  "resourceType" : "SearchParameter",
  "id" : "example-constraint",
  "extension" : [{
    "url" : "http://hl7.org/fhir/StructureDefinition/structuredefinition-wg",
    "valueCode" : "fhir"
  }],
  "url" : "http://hl7.org/fhir/SearchParameter/example-constraint",
  "name" : "Exampleconstraint",
  "title" : "example-constraint",
  "status" : "draft",
  "experimental" : true,
  "publisher" : "HL7 International / FHIR Infrastructure",
  "contact" : [{
    "telecom" : [{
      "system" : "url",
      "value" : "http://www.hl7.org/Special/committees/fiwg"
    }]
  }],
  "description" : "Search Composition Bundle",
  "code" : "example-constraint",
  "base" : ["Bundle"],
  "type" : "reference",
  "expression" : "Bundle.entry[0].resource",
  "processingMode" : "normal",
  "constraint" : "Bundle.type = 'document' and Bundle.entry[0].resource is Composition",
  "target" : ["Composition"]
}