@mapmany missing?

使用 QuerySQLite 和 SQLite 重现 issue 中的管道，然后将缺失的 mapmany 调用与 QueryOperators 的 enumerable_mapmany.jl 实现进行比较。阅读 standalone_query_macros.jl 中生成的调用，并确定 SQLite 源码在哪个位置未能支持该调用。当 groupby、split 和 mapmany 示例成功运行时，即表示完成。

Using master, it looks like the @mapmany command is missing. For the groupby and then split approach mapmany is critical, is it just not implemented? I didn't see it mentioned in the codebase.

julia> db = SQLite.DB("data.sqlite3");

julia> getproperty(db, tbl[1]) |>
    @groupby(_.cell_id) |>
     # filter stuff
    @map({cell_id=key(_), rows=_}) |>
    @mapmany(i->i.rows, (i, j)->{j...}) |>
    DataFrame;
MethodError: no method matching mapmany(::QuerySQLite.SourceCode{SQLite.DB}, ::var"#113#123", ::Expr, ::var"#114#124", ::Expr)
Closest candidates are:
  mapmany(!Matched::QueryOperators.Enumerable, ::Function, ::Expr, ::Function, ::Expr) at /home/tlnagy/.julia/packages/QueryOperators/g4G21/src/enumerable/enumerable_mapmany.jl:42

Stacktrace:
 [1] (::var"#112#122")(::QuerySQLite.SourceCode{SQLite.DB}) at /home/tlnagy/.julia/packages/Query/AwBtd/src/standalone_query_macros.jl:205
 [2] |>(::QuerySQLite.SourceCode{SQLite.DB}, ::var"#112#122") at ./operators.jl:823
 [3] top-level scope at In[30]:1