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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(filename, mesh, file_format=None, **kwargs):
 """Writes mesh together with data to a file. :params filename: File to write to. :type filename: str :params point_data: Named additional point data to write to the file. :type point_data: dict """

    if not file_format:
        # deduce file format from extension
        file_format = _filetype_from_filename(filename)

    # check cells for sanity
    for key, value in mesh.cells.items():
        if key[:7] == "polygon":
            assert value.shape[1] == int(key[7:])
        else:
            assert value.shape[1] == num_nodes_per_cell[key]

    try:
        interface, args, default_kwargs = _writer_map[file_format]
    except KeyError:
        raise KeyError(
            "Unknown format '{}'. Pick one of {}".format(
                file_format, sorted(list(_writer_map.keys()))
            )
        )

    # Build kwargs
    _kwargs = default_kwargs.copy()
    _kwargs.update(kwargs)

    # Write
    return interface.write(filename, mesh, *args, **_kwargs)