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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 write( unparser, nodes, output_stream, sourcemap_stream=None, sourcemap_normalize_mappings=True, sourcemap_normalize_paths=True, source_mapping_url=NotImplemented):
 """ Write out the node using the unparser into an output stream, and optionally the sourcemap using the sourcemap stream. Ideally, file objects should be passed to the *_stream arguments, so that the name resolution built into the sourcemap builder function will be used. Also, if these file objects are opened using absolute path arguments, enabling the sourcemap_normalize_paths flag will have all paths normalized to their relative form. If the provided streams are not anchored on the filesystem, or that the provide node was generated from a string or in-memory stream, the generation of the sourcemap should be done using the lower level `write` function provided by the sourcemap module, which this method wraps. Alternatively, the top level node should have its sourcepath set to path that this node originated from. Arguments unparser An unparser instance. nodes The Node or list of Nodes to stream to the output stream with the unparser. output_stream Either a stream object or a callable that produces one. The stream object to write to; its 'write' method will be invoked. If a callable was provided, the 'close' method on its return value will be called to close the stream. sourcemap_stream If one is provided, the sourcemap will be written out to it. Like output_stream, it could also be a callable and be handled in the same manner. If this argument is the same as output_stream (note: the return value of any callables are not compared), the stream object that is the same as the output_stream will be used for writing out the source map, and the source map will instead be encoded as a 'data:application/json;base64,' URL. sourcemap_normalize_mappings Flag for the normalization of the sourcemap mappings; Defaults to True to enable a reduction in output size. sourcemap_normalize_paths If set to true, all absolute paths will be converted to the relative form when the sourcemap is generated, if all paths provided are in the absolute form. Defaults to True to enable a reduction in output size. source_mapping_url If unspecified, the default derived path will be written as a sourceMappingURL comment into the output stream. If explicitly specified with a value, that will be written instead. Set to None to disable this. """


    closer = []

    def get_stream(stream):
        if callable(stream):
            result = stream()
            closer.append(result.close)
        else:
            result = stream
        return result

    def cleanup():
        for close in reversed(closer):
            close()

    chunks = None
    if isinstance(nodes, Node):
        chunks = unparser(nodes)
    elif isinstance(nodes, Iterable):
        raw = [unparser(node) for node in nodes if isinstance(node, Node)]
        if raw:
            chunks = chain(*raw)

    if not chunks:
        raise TypeError('must either provide a Node or list containing Nodes')

    try:
        out_s = get_stream(output_stream)
        sourcemap_stream = (
            out_s if sourcemap_stream is output_stream else sourcemap_stream)
        mappings, sources, names = sourcemap.write(
            chunks, out_s, normalize=sourcemap_normalize_mappings)
        if sourcemap_stream:
            sourcemap_stream = get_stream(sourcemap_stream)
            sourcemap.write_sourcemap(
                mappings, sources, names, out_s, sourcemap_stream,
                normalize_paths=sourcemap_normalize_paths,
                source_mapping_url=source_mapping_url,
            )
    finally:
        cleanup()