@Library('something')
import com.something.MySomething

def list = MySomething.getList()

pipeline {
    agent any
    parameters {
        choice(name: 'CHOICE', choices: list, description: 'Pick something')
    }
    stages {
        stage('Example') {
            steps {
                echo "Choice: ${params.CHOICE}"
            }
        }
    }
}