I want to manually enter the version of SVN that I need to build,but parameter doesn't work.

pipeline{
agent any
parameters{
string(name:'svn',defaultValue:'HEAD', description: '请输入svn编号，默认为最新' )
}
stages {
stage('代码获取') {
steps {
checkout([$class: 'SubversionSCM', additionalCredentials: [], excludedCommitMessages: '', excludedRegions: '', excludedRevprop: '', excludedUsers: '', filterChangelog: false, ignoreDirPropChanges: false, includedRegions: '', locations: [[cancelProcessOnExternalsFail: true, credentialsId: '****', depthOption: 'infinity', ignoreExternalsOption: true, local: '.', remote: 'svn_url@${params.svn}']], quietOperation: true, workspaceUpdater: [$class: 'UpdateUpdater']])
}
}
}
}