#---------- Python capability-based polymorphism----------#
def toDOM(xml_src=None):
    from xml.dom import minidom
    if hasattr(xml_src, 'documentElement'):
        return xml_src    # it is already a DOM object
    elif hasattr(xml_src,'read'):
        # it is something that knows how to read data
        return minidom.parseString(xml_src.read())
    elif type(xml_src) in (StringType, UnicodeType):
        # it is a filename of an XML document
        xml = open(xml_src).read()
        return minidom.parseString(xml)
    else:
        raise ValueError, "Must be initialized with " +\
              "filename, file-like object, or DOM object"