Creates a circle
        @type  cx: string or int
        @param cx:  starting x-coordinate  
        @type  cy: string or int
        @param cy:  starting y-coordinate 
        @type  r: string or int
        @param r:  radius 
        @type  strokewidth: string or int
        @param strokewidth:  width of the pen used to draw
        @type  stroke: string (either css constants like "black" or numerical values like "#FFFFFF")
        @param stroke:  color with which to draw the outer limits
        @type  fill: string (either css constants like "black" or numerical values like "#FFFFFF")
        @param fill:  color with which to fill the element (default: no filling)
        @return:  a circle object

def createCircle(self, cx, cy, r, strokewidth=1, stroke='black', fill='none'):
        """
        Creates a circle
        @type  cx: string or int
        @param cx:  starting x-coordinate  
        @type  cy: string or int
        @param cy:  starting y-coordinate 
        @type  r: string or int
        @param r:  radius 
        @type  strokewidth: string or int
        @param strokewidth:  width of the pen used to draw
        @type  stroke: string (either css constants like "black" or numerical values like "#FFFFFF")
        @param stroke:  color with which to draw the outer limits
        @type  fill: string (either css constants like "black" or numerical values like "#FFFFFF")
        @param fill:  color with which to fill the element (default: no filling)
        @return:  a circle object
        """
        style_dict = {'fill':fill, 'stroke-width':strokewidth, 'stroke':stroke}
        myStyle = StyleBuilder(style_dict)
        c = Circle(cx, cy, r)
        c.set_style(myStyle.getStyle())
        return c