code: public function get(string $environment): ConfigInterface
      {
          if (!isset($this->configMappings[$environment])) {
              throw ConfigException::createByEnvironment($environment);
          }
  
          if (!isset($this->configs[$environment])) {
              $class = $this->configMappings[$environment];
  
              $this->configs[$environment] = $class::create($this->rootDir);
          }
  
          return $this->configs[$environment];
      }
docs: @param string $environment
  
  @return ConfigInterface
  
  @throws ConfigException