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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 DocbookXInclude(env, target, source, *args, **kw):
 """ A pseudo-Builder, for resolving XIncludes in a separate processing step. """

    # Init list of targets/sources
    target, source = __extend_targets_sources(target, source)

    # Setup builder
    __builder = __select_builder(__xinclude_lxml_builder,__xinclude_libxml2_builder,__xmllint_builder)
            
    # Create targets
    result = []
    for t,s in zip(target,source):
        result.extend(__builder.__call__(env, t, s, **kw))
        
    return result