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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def importElementTree(module_names=None):
 """Find a working ElementTree implementation, trying the standard places that such a thing might show up. @param module_names: The names of modules to try to use as ElementTree. Defaults to C{L{elementtree_modules}} @returns: An ElementTree module """

    if module_names is None:
        module_names = elementtree_modules

    for mod_name in module_names:
        try:
            ElementTree = __import__(mod_name, None, None, ['unused'])
        except ImportError:
            pass
        else:
            # Make sure it can actually parse XML
            try:
                ElementTree.XML('<unused/>')
            except (SystemExit, MemoryError, AssertionError):
                raise
            except:
                logging.exception('Not using ElementTree library %r because it failed to '
                    'parse a trivial document: %s' % mod_name)
            else:
                return ElementTree
    else:
        raise ImportError('No ElementTree library found. '
                          'You may need to install one. '
                          'Tried importing %r' % (module_names,)
                          )