class Geometry:
    """
    base class for all geometry
    """
    def project(self, proj):
        """
        project geometry
        """
        raise NotImplementedError('project() is not implemented')
    
    def bbox(self):
        raise NotImplementedError('bbox() is not implemented')
    
    def project(self, proj):
        raise NotImplementedError('project() is not implemented')
    
    def project_view(self, view):
        raise NotImplementedError('project_view() is not implemented')
        
    def to_svg(self, round=0):
        raise NotImplementedError('to_svg() is not implemented')
        
    def crop_to(self, view_bounds):
        raise NotImplementedError('crop_to() is not implemented')

    def substract_geom(self, geom):
        raise NotImplementedError('substract_geom() is not implemented yet')
        
    def is_emtpy(self):
        return False
        
    def unify(self, point_store, precision=None):
        raise NotImplementedError('unify() is not implemented yet')
        
    def points(self):
        """
        returns a list of point lists
        """
        raise NotImplementedError('points() is not implemented yet')
        
    def join(self, geom):
        raise NotImplementedError('join() is not implemented yet')
        

    
class SolidGeometry(Geometry):
    """
    base class for all solid geometry, e.g. polygons
    """
    def area():
        """
        calculates area for this geometry
        """
        raise NotImplementedError('area() is not implemented')
        
    def centroid():
        """
        calculates centroid for this geometry
        """
        raise NotImplementedError('centroid() is not implemented')
    
    def invalidate(self):
        self.__area = None