what's wrong in my code to Create a PolygonalFaceSet Geometry?

[Huzhengyang93]

`DatabaseIfc db = new DatabaseIfc(ModelView.Ifc4X3NotAssigned);
IfcProject project = new IfcProject(db, "IfcPolygonalFaceSet Example");

IfcObjectPlacement objectplacement = new IfcLocalPlacement(new IfcAxis2Placement3D(new IfcCartesianPoint(db, 0, 0)));
var coordinates = new List<Tuple<double, double, double>>
{
new Tuple<double,double,double> ( 0, 0, 0 ),
new Tuple<double,double,double> (10, 0, 0),
new Tuple<double,double,double> (10, 0, 3),
new Tuple<double,double,double> (0, 0, 3),
new Tuple<double,double,double> (2.5, 4, 1.5)
};

var pointList = new IfcCartesianPointList3D(db, coordinates);

var faces = new List<Tuple<int, int, int>>
{
new Tuple< int, int, int >( 0, 1, 4 ),
new Tuple< int, int, int > (1, 2, 4),
new Tuple< int, int, int > (2, 3, 4),
new Tuple< int, int, int > (3, 0, 4),
new Tuple< int, int, int > (0, 3, 2),
new Tuple< int, int, int > (2, 1, 0)
};

List facelist = new List();
foreach (var item in faces)
{
IfcIndexedPolygonalFace face = new IfcIndexedPolygonalFace(db, item.Item1, item.Item2, item.Item3);
facelist.Add(face);
}
IfcPolygonalFaceSet polygonalIT = new IfcPolygonalFaceSet(pointList, facelist);
IfcShapeRepresentation shapeRepresentation1 = new IfcShapeRepresentation(polygonalIT);
IfcProductDefinitionShape shape1 = new IfcProductDefinitionShape(shapeRepresentation1);
var geo = new IfcGeomodel(project, objectplacement, shape1);

db.WriteFile(filefullname);`

by this code I want to create a pyramid Geometry,but got a plane