indent is non-
null, the converter attempts to "pretty-print" the
JSON, and uses
indent as the indentation. Otherwise the result has no
whitespace outside of string literals.
indent contains characters that are not valid JSON whitespace
characters, the result will not be valid JSON. JSON whitespace characters
are space (U+0020), tab (U+0009), line feed (U+000a) and carriage return
bufferSize is the size of the internal buffers used to collect
UTF-8 code units.
If using startChunkedConversion, it will be the size of the chunks.
The JSON encoder handles numbers, strings, booleans, null, lists and maps directly.
Any other object is attempted converted by
toEncodable to an object that
is of one of the convertible types.
toEncodable is omitted, it defaults to calling
.toJson() on the