def fit(self, signal) -> "CostLinear":
        """Set parameters of the instance. The first column contains the
        observed variable. The other columns contains the covariates.

        Args:
            signal (array): signal of shape (n_samples, n_regressors+1)

        Returns:
            self
        """
        assert signal.ndim > 1, "Not enough dimensions"

        self.signal = signal[:, 0].reshape(-1, 1)
        self.covar = signal[:, 1:]
        return self
Set parameters of the instance. The first column contains the
        observed variable. The other columns contains the covariates.

        Args:
            signal (array): signal of shape (n_samples, n_regressors+1)

        Returns:
            self
        
src/ruptures/costs/costlinear.py