Constant COUPLING 

pub const COUPLING: &str = "Rank symbols by DIRECTED call coupling over `calls` edges: `fan_in` (how many distinct \
    symbols call this one), `fan_out` (how many it calls), `instability` = \
    fan_out/(fan_in+fan_out). `order`=fan_in finds what the codebase most depends on, \
    `order`=fan_out the symbols that reach furthest, `total` (the default) overall coupling. \
    Call edges are resolved by simple name, so a short generically-named function can absorb \
    every call to that name — say so if you report a high `fan_in` on one. `limit` is 1-100 \
    (default 20) — no unlimited setting.";

coupling.