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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 yield_nanopub(assertions, annotations, line_num):
 """Yield nanopub object"""


    if not assertions:
        return {}

    anno = copy.deepcopy(annotations)

    evidence = anno.pop("evidence", None)
    stmt_group = anno.pop("statement_group", None)
    citation = anno.pop("citation", None)

    anno_list = []
    for anno_type in anno:
        if isinstance(anno[anno_type], (list, tuple)):
            for val in anno[anno_type]:
                anno_list.append({"type": anno_type, "label": val})
        else:
            anno_list.append({"type": anno_type, "label": anno[anno_type]})

    assertions_list = []
    for assertion in assertions:
        (subj, rel, obj) = split_bel_stmt(assertion, line_num)
        assertions_list.append({"subject": subj, "relation": rel, "object": obj})

    nanopub = {
        "schema_uri": "https://raw.githubusercontent.com/belbio/schemas/master/schemas/nanopub_bel-1.0.0.yaml",
        "type": copy.deepcopy(nanopub_type),
        "annotations": copy.deepcopy(anno_list),
        "citation": copy.deepcopy(citation),
        "assertions": copy.deepcopy(assertions_list),
        "evidence": evidence,
        "metadata": {"statement_group": stmt_group},
    }

    return {"nanopub": copy.deepcopy(nanopub)}