def _partial_corr(self, x=None, y=None, covar=None, x_covar=None, y_covar=None,
                  tail='two-sided', method='pearson'):
    """Partial and semi-partial correlation."""
    stats = partial_corr(data=self, x=x, y=y, covar=covar, x_covar=x_covar,
                         y_covar=y_covar, tail=tail, method=method)
    return stats
Partial and semi-partial correlation.