'write drawings for one sheet in one file'

def write(self):

    root = Element('xdr:wsDr', {'xmlns:xdr': 'http://schemas.openxmlformats.org/drawingml/2006/spreadsheetDrawing', 'xmlns:a': 'http://schemas.openxmlformats.org/drawingml/2006/main'})
    for (i, chart) in enumerate(self._sheet._charts):
        drawing = chart.drawing
        (x, y, w, h) = drawing.get_emu_dimensions()
        anchor = SubElement(root, 'xdr:absoluteAnchor')
        SubElement(anchor, 'xdr:pos', {'x': str(x), 'y': str(y)})
        SubElement(anchor, 'xdr:ext', {'cx': str(w), 'cy': str(h)})
        frame = SubElement(anchor, 'xdr:graphicFrame', {'macro': ''})
        name = SubElement(frame, 'xdr:nvGraphicFramePr')
        SubElement(name, 'xdr:cNvPr', {'id': ('%s' % i), 'name': ('Graphique    %s' % i)})
        SubElement(name, 'xdr:cNvGraphicFramePr')
        frm = SubElement(frame, 'xdr:xfrm')
        SubElement(frm, 'a:off', {'x': '0', 'y': '0'})
        SubElement(frm, 'a:ext', {'cx': '0', 'cy': '0'})
        graph = SubElement(frame, 'a:graphic')
        data = SubElement(graph, 'a:graphicData', {'uri': 'http://schemas.openxmlformats.org/drawingml/2006/chart'})
        SubElement(data, 'c:chart', {'xmlns:c': 'http://schemas.openxmlformats.org/drawingml/2006/chart', 'xmlns:r': 'http://schemas.openxmlformats.org/officeDocument/2006/relationships', 'r:id': ('rId%s' % (i + 1))})
        SubElement(anchor, 'xdr:clientData')
    return get_document_content(root)
