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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 load_notebook_node(notebook_path):
 """Returns a notebook object with papermill metadata loaded from the specified path. Args: notebook_path (str):
 Path to the notebook file. Returns: nbformat.NotebookNode """

    nb = nbformat.reads(papermill_io.read(notebook_path), as_version=4)

    if not hasattr(nb.metadata, 'papermill'):
        nb.metadata['papermill'] = {
            'parameters': dict(),
            'environment_variables': dict(),
            'version': __version__,
        }

    for cell in nb.cells:
        if not hasattr(cell.metadata, 'tags'):
            cell.metadata['tags'] = []  # Create tags attr if one doesn't exist.

        if not hasattr(cell.metadata, 'papermill'):
            cell.metadata['papermill'] = dict()
    return nb