Checks whether all the attributes of this object is valid.

def _validate(self):
        """
        Checks whether all the attributes of this object is valid.
        """
        if self.region_type not in regions_attributes:
            raise ValueError("'{0}' is not a valid region type in this package"
                             .format(self.region_type))

        if self.coordsys not in valid_coordsys['DS9'] + valid_coordsys['CRTF']:
            raise ValueError("'{0}' is not a valid coordinate reference frame "
                             "in astropy".format(self.coordsys))