def _search_doc(search_str, doc_dict):
    """Search the documentation.

    Parameters
    ----------
    search_str : string
        string to search for (str)
    doc_dict : dict
        documentation dict to search in(dict

    """
    rtn = []
    for k in list(doc_dict.keys()):
        if k.lower().find(search_str.lower()) > -1 or doc_dict[k].lower().find(
            search_str.lower()) > -1:
            rtn.append(k)
    return rtn
