Function load 

pub fn load(
    working_directory: &Path,
    environment: &Environment,
    flags: &Layer,
) -> Result<Loaded, ConfigError>

Load the configuration: documents, then the environment, then flags.

Each source’s config block is checked against its plugin’s declared schema before this returns, so a mistyped per-source field is a load-time refusal rather than a surprise inside the first call that source makes.

Errors

Returns ConfigError for a document that cannot be read or parsed, and for any setting that is unknown, unusable, or names a plugin this build does not have.