// Package errdefs defines a set of error interfaces that packages should use for communicating classes of errors.
 // Errors that cross the package boundary should implement one (and only one) of these interfaces.
 //
 // Packages should not reference these interfaces directly, only implement them.
 // To check if a particular error implements one of these interfaces, there are helper
 // functions provided (e.g. `Is<SomeError>`) which can be used rather than asserting the interfaces directly.
 // If you must assert on these interfaces, be sure to check the causal chain (`err.Cause()`).
 package errdefs