code: private function _keyExists($propName): bool
  	{
  		if (array_key_exists($propName, $this->_map)) {
  			$propName = $this->_map[$propName];
  		}
  
  		return in_array($propName, $this->_publicNames);
  	}
docs: Returns true if key/prop name exists or is mappable.
  
  @param string $propName
  
  @return bool