Function that gets vectors of the pdf and target at the last design
        evaluated.

        :return: tuple of q values, pdf values, target values

def getPDF(self):
        '''Function that gets vectors of the pdf and target at the last design
        evaluated.

        :return: tuple of q values, pdf values, target values
        '''

        if hasattr(self, '_qplot'):

            return self._qplot, self._hplot, self._tplot

        else:
            raise ValueError('''The metric has not been evaluated at any
                    design point so the PDF cannot get obtained''')