code: protected function parse_user() {
  
  		if ( ! empty( $this->args['user'] ) ) {
  			$this->args['user__in'] = array( $this->args['user'] );
  		}
  
  		return $this->parse_in_or_not_in_query( 'user', $this->args['user__in'], $this->args['user__not_in'] );
  	}
docs: Parse the user where.
  
  @since 1.0
  
  @return Where|null