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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 get_compounds(identifier, namespace='cid', searchtype=None, as_dataframe=False, **kwargs):
 """Retrieve the specified compound records from PubChem. :param identifier: The compound identifier to use as a search query. :param namespace: (optional) The identifier type, one of cid, name, smiles, sdf, inchi, inchikey or formula. :param searchtype: (optional) The advanced search type, one of substructure, superstructure or similarity. :param as_dataframe: (optional) Automatically extract the :class:`~pubchempy.Compound` properties into a pandas :class:`~pandas.DataFrame` and return that. """

    results = get_json(identifier, namespace, searchtype=searchtype, **kwargs)
    compounds = [Compound(r) for r in results['PC_Compounds']] if results else []
    if as_dataframe:
        return compounds_to_frame(compounds)
    return compounds