How to use the fastparquet.writer.partition_on_columns function in fastparquet

fmd=None,
        compression=None,
        **kwargs
    ):
        fmd = copy.copy(fmd)
        if not len(df):
            # Write nothing for empty partitions
            rgs = []
        elif partition_on:
            mkdirs = lambda x: fs.mkdirs(x, exist_ok=True)
            if LooseVersion(fastparquet.__version__) >= "0.1.4":
                rgs = partition_on_columns(
                    df, partition_on, path, filename, fmd, compression, fs.open, mkdirs
                )
            else:
                rgs = partition_on_columns(
                    df,
                    partition_on,
                    path,
                    filename,
                    fmd,
                    fs.sep,
                    compression,
                    fs.open,
                    mkdirs,
                )
        else:
            with fs.open(fs.sep.join([path, filename]), "wb") as fil:
                fmd.num_rows = len(df)
                rg = make_part_file(
                    fil, df, fmd.schema, compression=compression, fmd=fmd
                )

import fastparquet

    # Fastparquet mutates this in a non-threadsafe manner. For now we just copy
    # it before forwarding to fastparquet.
    fmd = copy.copy(fmd)
    if not len(df):
        # Write nothing for empty partitions
        rgs = None
    elif partition_on:
        mkdirs = lambda x: fs.mkdirs(x, exist_ok=True)
        if LooseVersion(fastparquet.__version__) >= "0.1.4":
            rgs = partition_on_columns(
                df, partition_on, path, filename, fmd, compression, fs.open, mkdirs
            )
        else:
            rgs = partition_on_columns(
                df,
                partition_on,
                path,
                filename,
                fmd,
                fs.sep,
                compression,
                fs.open,
                mkdirs,
            )
    else:
        # Fastparquet current doesn't properly set `num_rows` in the output
        # metadata. Set it here to fix that.
        fmd.num_rows = len(df)
        with fs.open(fs.sep.join([path, filename]), "wb") as fil:
            rgs = make_part_file(fil, df, fmd.schema, compression=compression, fmd=fmd)

def _write_partition_fastparquet(
    df, fs, path, filename, fmd, compression, partition_on
):
    from fastparquet.writer import partition_on_columns, make_part_file
    import fastparquet

    # Fastparquet mutates this in a non-threadsafe manner. For now we just copy
    # it before forwarding to fastparquet.
    fmd = copy.copy(fmd)
    if not len(df):
        # Write nothing for empty partitions
        rgs = None
    elif partition_on:
        mkdirs = lambda x: fs.mkdirs(x, exist_ok=True)
        if LooseVersion(fastparquet.__version__) >= "0.1.4":
            rgs = partition_on_columns(
                df, partition_on, path, filename, fmd, compression, fs.open, mkdirs
            )
        else:
            rgs = partition_on_columns(
                df,
                partition_on,
                path,
                filename,
                fmd,
                fs.sep,
                compression,
                fs.open,
                mkdirs,
            )
    else:
        # Fastparquet current doesn't properly set `num_rows` in the output

fs,
        filename,
        partition_on,
        return_metadata,
        fmd=None,
        compression=None,
        **kwargs
    ):
        fmd = copy.copy(fmd)
        if not len(df):
            # Write nothing for empty partitions
            rgs = []
        elif partition_on:
            mkdirs = lambda x: fs.mkdirs(x, exist_ok=True)
            if LooseVersion(fastparquet.__version__) >= "0.1.4":
                rgs = partition_on_columns(
                    df, partition_on, path, filename, fmd, compression, fs.open, mkdirs
                )
            else:
                rgs = partition_on_columns(
                    df,
                    partition_on,
                    path,
                    filename,
                    fmd,
                    fs.sep,
                    compression,
                    fs.open,
                    mkdirs,
                )
        else:
            with fs.open(fs.sep.join([path, filename]), "wb") as fil: