kcl run --format toml returns wrong data

[diefans]

Bug Report

Using the --format toml option to render TOML instead of YAML returns a wrong result.
Seems like there is a custom/naive toml serializer in place...

1. Minimal reproduce step (Required)

kcl run --format toml /dev/stdin << EOF
schema Bar:

schema Foo:
    b: Bar
    a: str = "a"

Foo {
    b: Bar {}
}
EOF

2. What did you expect to see? (Required)

a = "a"

[b]

3. What did you see instead (Required)

[b]
a = "a"

4. What is your KCL components version? (Required)

kcl version is v0.10.8