code: public function getClient()
  	{
  		if ($this->_client === null) {
  			$settings=[
  				'key' => $this->key,
  				'secret' => $this->secret
  			];
  			if($this->enableV4)
  				$settings['signature']='v4';
  			
  			$this->_client = S3Client::factory($settings);
  		}
  		return $this->_client;
  	}
docs: Returns a S3Client instance
  @return \Aws\S3\S3Client