#[derive(Debug, thiserror::Error)]
pub enum Error {
#[error("I/O {0}")]
Io(#[from] std::io::Error),
#[error("Invalid branches: {0}")]
InvalidBranches(String),
#[error("Unknown branch label: {0}")]
UnknownBranchLabel(String),
}
pub type Result<T> = std::result::Result<T, Error>;