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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 export_dict(mesh, encoding=None):
 """ Export a mesh to a dict Parameters mesh : Trimesh object Mesh to be exported encoding : str, or None 'base64' Returns """


    def encode(item, dtype=None):
        if encoding is None:
            return item.tolist()
        else:
            if dtype is None:
                dtype = item.dtype
            return util.array_to_encoded(item, dtype=dtype, encoding=encoding)

    # metadata keys we explicitly want to preserve
    # sometimes there are giant datastructures we don't
    # care about in metadata which causes exports to be
    # extremely slow, so skip all but known good keys
    meta_keys = ['units', 'file_name', 'file_path']
    metadata = {k: v for k, v in mesh.metadata.items() if k in meta_keys}

    export = {
        'metadata': metadata,
        'faces': encode(mesh.faces),
        'face_normals': encode(mesh.face_normals),
        'vertices': encode(mesh.vertices)
    }
    if mesh.visual.kind == 'face':
        export['face_colors'] = encode(mesh.visual.face_colors)
    elif mesh.visual.kind == 'vertex':
        export['vertex_colors'] = encode(mesh.visual.vertex_colors)

    return export