This wraps AcDbSpline::AcDbSpline() method

Public Sub New(
    fitPoints As Point3dCollection, 
    startTangent As Vector3d, 
    endTangent As Vector3d, 
    knotParam As KnotParameterizationEnum, 
    degree As Integer, 
    fitTolerance As double
)

public Spline(
    Point3dCollection fitPoints, 
    Vector3d startTangent, 
    Vector3d endTangent, 
    KnotParameterizationEnum knotParam, 
    int degree, 
    double fitTolerance
);