Returns angle specified by three sites.

        Args:
            i: Index of first site.
            j: Index of second site.
            k: Index of third site.

        Returns:
            Angle in degrees.

def get_angle(self, i: int, j: int, k: int) -> float:
        """
        Returns angle specified by three sites.

        Args:
            i: Index of first site.
            j: Index of second site.
            k: Index of third site.

        Returns:
            Angle in degrees.
        """
        v1 = self[i].coords - self[j].coords
        v2 = self[k].coords - self[j].coords
        return get_angle(v1, v2, units="degrees")