Python SVG small custom lib

class SVG:
    def __init__(self, width, height):
        self.width = width
        self.height = height
        self.objects = []

    def serialize(self):
        lines = []
        lines.append('<svg version="1.1" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="'+str(self.width)+'" height="'+str(self.height)+'" viewBox="0 0 '+str(self.width)+' '+str(self.height)+'">\n')
        for i in range(len(self.objects)):
            lines.extend(map(lambda x:'\t'+x, self.objects[i].serialize()))
        lines.append('</svg>')

        return lines

    def save(self, file):
        provided = True
        if isinstance(file, str):
            file = open(file, "w")
            provided = False

        file.writelines(self.serialize())

        if not provided:
            file.close()

        return file

    def add(self, object, uptop=False):
        if uptop:
            self.objects.insert(0, object)
        else:
            self.objects.append(object)

        return self


class SVGGroup:
    def __init__(self, translate=None, rotate=None, scale=None, origin=None):
        self.objects = []
        self.translate = translate
        self.rotate = rotate
        self.scale = scale
        self.origin = origin

    def add(self, object, uptop=False):
        if uptop:
            self.objects.insert(0, object)
        else:
            self.objects.append(object)

        return self

    def serialize(self):
        lines = []
        text = '<g'
        if self.translate is not None or (self.rotate is not None and self.rotate!=0) or self.scale is not None:
            text = text + ' transform="'
            space = ''
            if self.origin is not None:
                text = text + space + 'translate' + str(self.origin)
                space = ' '
            if self.rotate is not None and self.rotate!=0:
                text = text + space + 'rotate('+str(self.rotate) + ')'
                space = ' '
            if self.scale is not None:
                if isinstance(self.scale, tuple):
                    text = text + space + 'scale' + str(self.scale)
                else:
                    text = text + space + 'scale(' + str(self.scale) + ')'
                space = ' '
            if self.translate is not None:
                if self.origin is not None:
                    text = text + space + 'translate(' + str(-self.origin[0]+self.translate[0]) + ', ' + str(-self.origin[1]+self.translate[1]) + ')'
                else:
                    text = text + space + 'translate' + str(self.translate)

            text = text + '"'
        text = text + '>\n'
        lines.append(text)

        for i in range(len(self.objects)):
            lines.extend(map(lambda x:'\t' + x, self.objects[i].serialize()))

        lines.append('</g>\n')

        return lines


class SVGLine:
    def __init__(self, start, end, stroke_width, color, linecap="butt"):
        self.x1 = start[0]
        self.y1 = start[1]
        self.x2 = end[0]
        self.y2 = end[1]
        self.stroke_width = stroke_width
        self.color = color
        self.stroke_linecap = linecap #butt/round/square
        #self.stroke_dasharray = stroke_dasharray #tupple of lengths of segment and spaces

    def serialize(self):
        text = '<line x1="'+str(self.x1)+'" y1="'+str(self.y1)+'" x2="'+str(self.x2)+'" y2="'+str(self.y2)+'" stroke="'+self.color+'" stroke-width="'+str(self.stroke_width)+'"'
        if self.stroke_linecap!="butt":
            text = text + ' stroke-linecap="'+self.stroke_linecap+'"'
        text = text + '/>\n'
        return [text]


def Color(r, g, b, a=1):
    if a==1:
        return "rgb(" + str(r) + "," + str(g) + "," + str(b) + ")"
    else:
        return "rgb(" + str(r) + "," + str(g) + "," + str(b) + "," + str(a) + ")"