Function to_writer_pretty 

pub fn to_writer_pretty<W, T>(
    writer: W,
    value: &T,
    config: PrettyConfig,
) -> Result<()>
where
    W: Write,
    T: ?Sized + Serialize,

Serializes value into writer in a pretty way.

writer is required to implement core::fmt::Write. To use std::io::Write instead, see Options::to_io_writer_pretty.