Draw a drawing with two boxes, each with a name inside
            and a polyline between the midpoints of the sides of the boxes,
            with half-way the polyline a rhombus with an id included.

def Draw_a_drawing_of_one_sheet(self, nr_of_boxes, box_names):
        """ Draw a drawing with two boxes, each with a name inside
            and a polyline between the midpoints of the sides of the boxes,
            with half-way the polyline a rhombus with an id included.
        """
        thickness = 2  # Line thickness
        center_x = []    # x of the center of box[i] on canvas
        center_y = []    # y of the center of box[i] on canvas
        mid_points = []
        box_width = 100  # pixels
        box_height = 100  # pixels
        delta_x = self.screen_width / (nr_of_boxes + 1)
        delta_y = self.screen_height / (nr_of_boxes + 1)
        # Draw the boxes
        for box_nr in range(0, nr_of_boxes):
            center_x.append(delta_x + box_nr * delta_x)
            center_y.append(delta_y + box_nr * delta_y)
            name = box_names[box_nr]
            ident = str(box_nr + 1)
            # Draw one box at the specified location
            mid_points.append(self.box_type_1(
                center_x[box_nr], center_y[box_nr],
                name, ident, box_width,box_height))

        # Draw a line with arrow head to the first box
        x2 = mid_points[0][3][0]
        y2 = mid_points[0][3][1]
        x1 = x2 - 150
        y1 = y2
        line_0 = gui.SvgLine(x1, y1, x2, y2)
        line_0.set_stroke(width=thickness, color='black')
        self.sheet.append(line_0)
        # Add an arrow head to line_0
        head_0 = SvgPolygon(4)
        arrow_height = 20
        arrow_width = arrow_height / 3
        recess = arrow_height / 5
        head_0.add_arrow_coord(line_0, arrow_height, arrow_width, recess)
        head_0.set_stroke(width=thickness, color='black')
        head_0.set_fill(color='blue')
        self.sheet.append(head_0)

        # Draw a rhombus polygon
        x = (center_x[0] + center_x[1]) / 2
        y = (center_y[0] + center_y[1]) / 2
        self.int_id += 1
        str_id = str(self.int_id)
        hor_size = 15  # pixels
        vert_size = 25  # pixels
        rhombus = self.rhombus_polygon(x, y, str_id, hor_size, vert_size)

        # Determine points of the first polyline
        line_1_points = []
        line_1_points.append(mid_points[0][2])
        corner = [rhombus[0][0], mid_points[0][2][1]]
        line_1_points.append(corner)
        line_1_points.append(rhombus[0])
        # Draw a polyline from box_1 to rhombus
        line1 = gui.SvgPolyline(_maxlen=4)
        for pt in line_1_points:
            line1.add_coord(*pt)
        line1.set_stroke(width=thickness, color='black')
        self.sheet.append(line1)

        # Determine points of the second polyline
        line_2_points = []
        line_2_points.append(rhombus[1])
        corner = [rhombus[1][0], mid_points[1][3][1]]
        line_2_points.append(corner)
        line_2_points.append(mid_points[1][3])
        # Drawa polyline from rhombus to box_2
        line2 = gui.SvgPolyline(_maxlen=4)
        for pt in line_2_points:
            line2.add_coord(pt[0], pt[1])
        line2.set_stroke(width=thickness, color='black')
        self.sheet.append(line2)
        
        # Add an arrow head to line2
        head = SvgPolygon(4)
        head.add_arrow_coord(line2, arrow_height, arrow_width, recess)
        head.set_stroke(width=thickness, color='black')
        head.set_fill(color='blue')
        self.sheet.append(head)