'Convert an element tree into XML as string
@param tree: the element tree
@param xml_declaration: add an XML declaration to the output
@param pretty_print: provide pretty formatted output'

@staticmethod
def tostring(tree, xml_declaration=True, pretty_print=True):

    return etree.tostring(tree, xml_declaration=xml_declaration, encoding='utf-8', pretty_print=pretty_print)
