def _par_write(self, dirname):
        """
        Internal write function to write a formatted parameter file.

        :type dirname: str
        :param dirname: Directory to write the parameter file to.
        """
        filename = dirname + '/' + 'template_parameters.csv'
        with open(filename, 'w') as parfile:
            for template in self.templates:
                for key in template.__dict__.keys():
                    if key not in ['st', 'event']:
                        parfile.write(key + ': ' +
                                      str(template.__dict__[key]) + ', ')
                parfile.write('\n')
        return self
Internal write function to write a formatted parameter file.

        :type dirname: str
        :param dirname: Directory to write the parameter file to.