Classes/Console/Core/Kernel.php
public function initialize(string $runLevel = null)
    {
        if (!$this->initialized) {
            self::initializeCompatibilityLayer($this->classLoader);
            Scripts::baseSetup($this->bootstrap);
            $this->initialized = true;
        }
        if ($runLevel !== null) {
            $this->runLevel->runSequence($runLevel);
        }
    }
public function initialize(string $runLevel = null)
    {
        if (!$this->initialized) {
            self::initializeCompatibilityLayer($this->classLoader);
            Scripts::baseSetup($this->bootstrap);
            $this->initialized = true;
        }
        if ($runLevel !== null) {
            $this->runLevel->runSequence($runLevel);
        }
    }
This is useful to bootstrap the console application
without actually executing a command (e.g. during composer install)

@param string $runLevel
@throws Exception
@throws InvalidArgumentException