StructureDefinition for code

<?xml version="1.0" encoding="UTF-8"?>
<StructureDefinition xmlns="http://hl7.org/fhir"><id value="code"/><text ><status value="generated"/><div xmlns="http://www.w3.org/1999/xhtml">to do</div></text><extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-standards-status"><valueCode value="normative"/></extension><extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-normative-version"><valueCode value="4.0.0"/></extension><extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-type-characteristics"><valueCode value="can-bind"/></extension><extension url="http://hl7.org/fhir/StructureDefinition/structuredefinition-type-characteristics"><valueCode value="has-length"/></extension><url value="http://hl7.org/fhir/StructureDefinition/code"/><version value="5.0.0"/><name value="code"/><status value="active"/><experimental value="false"/><date value="2023年03月26日T15:21:02+11:00"/><publisher value="HL7 FHIR Standard"/><contact ><telecom ><system value="url"/><value value="http://hl7.org/fhir"/></telecom></contact><description value="code type: A string which has at least one character and no leading or trailing
 whitespace and where there is no whitespace other than single spaces in the contents"/><jurisdiction ><coding ><system value="http://unstats.un.org/unsd/methods/m49/m49.htm"/><code value="001"/><display value="World"/></coding></jurisdiction><fhirVersion value="5.0.0"/><kind value="primitive-type"/><abstract value="false"/><type value="code"/><baseDefinition value="http://hl7.org/fhir/StructureDefinition/string"/><derivation value="specialization"/><snapshot ><element id="code"><path value="code"/><short value="Primitive Type code"/><definition value="A string which has at least one character and no leading or trailing whitespace
 and where there is no whitespace other than single spaces in the contents"/><min value="0"/><max value="*"/><base ><path value="code"/><min value="0"/><max value="*"/></base><constraint ><key value="ele-1"/><severity value="error"/><human value="All FHIR elements must have a @value or children"/><expression value="hasValue() or (children().count() &gt; id.count())"/><source value="http://hl7.org/fhir/StructureDefinition/Element"/></constraint><isModifier value="false"/><isSummary value="false"/></element><element id="code.id"><path value="code.id"/><representation value="xmlAttr"/><short value="xml:id (or equivalent in JSON)"/><definition value="unique id for the element within a resource (for internal references)"/><min value="0"/><max value="1"/><base ><path value="Element.id"/><min value="0"/><max value="1"/></base><!-- Note: special primitive values have a FHIRPath system type. e.g. this is compiler
 magic (h) --><type ><extensionurl="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type"><valueUrlvalue="string"/></extension><code value="http://hl7.org/fhirpath/System.String"/></type><isModifier value="false"/><isSummary value="false"/></element><element id="code.extension"><path value="code.extension"/><short value="Additional content defined by implementations"/><definition value="May be used to represent additional information that is not part of the basic definition
 of the resource. To make the use of extensions safe and managable, there is a strict
 set of governance applied to the definition and use of extensions. Though any implementer
 can define an extension, there is a set of requirements that SHALL be met as part
 of the definition of the extension."/><comment value="There can be no stigma associated with the use of extensions by any application,
 project, or standard - regardless of the institution or jurisdiction that uses
 or defines the extensions. The use of extensions is what allows the FHIR specification
 to retain a core level of simplicity for everyone."/><alias value="extensions"/><alias value="user content"/><min value="0"/><max value="*"/><base ><path value="Element.extension"/><min value="0"/><max value="*"/></base><type ><code value="Extension"/></type><constraint ><key value="ele-1"/><severity value="error"/><human value="All FHIR elements must have a @value or children"/><expression value="hasValue() or (children().count() &gt; id.count())"/><source value="http://hl7.org/fhir/StructureDefinition/Element"/></constraint><constraint ><key value="ext-1"/><severity value="error"/><human value="Must have either extensions or value[x], not both"/><expression value="extension.exists() != value.exists()"/><source value="http://hl7.org/fhir/StructureDefinition/Extension"/></constraint><isModifier value="false"/><isSummary value="false"/></element><element id="code.value"><path value="code.value"/><representation value="xmlAttr"/><short value="Primitive value for code"/><definition value="Primitive value for code"/><min value="0"/><max value="1"/><base ><path value="string.value"/><min value="0"/><max value="1"/></base><!-- Note: special primitive values have a FHIRPath system type. e.g. this is compiler
 magic (i) --><type ><extensionurl="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type"><valueUrlvalue="code"/></extension><extensionurl="http://hl7.org/fhir/StructureDefinition/regex"><valueStringvalue="[^\s]+( [^\s]+)*"/></extension><code value="http://hl7.org/fhirpath/System.String"/></type><isModifier value="false"/><isSummary value="false"/></element></snapshot><differential ><element id="code"><path value="code"/><short value="Primitive Type code"/><definition value="A string which has at least one character and no leading or trailing whitespace
 and where there is no whitespace other than single spaces in the contents"/><min value="0"/><max value="*"/></element><element id="code.value"><path value="code.value"/><representation value="xmlAttr"/><short value="Primitive value for code"/><definition value="Primitive value for code"/><min value="0"/><max value="1"/><!-- Note: special primitive values have a FHIRPath system type. e.g. this is compiler
 magic (g) --><type ><extensionurl="http://hl7.org/fhir/StructureDefinition/structuredefinition-fhir-type"><valueUrlvalue="code"/></extension><extensionurl="http://hl7.org/fhir/StructureDefinition/regex"><valueStringvalue="[^\s]+( [^\s]+)*"/></extension><code value="http://hl7.org/fhirpath/System.String"/></type></element></differential></StructureDefinition>