It declares a generic function but defines no methods for it:
julia> function foo end
foo (generic function with 0 methods)
Typically, the only reason to do this is to attach a documentation string to the function (rather than to any particular method). I don’t see why they did it in SearchLight.jl (where the functions have no docstrings), except maybe as a form of code documentation or as a placeholder for them to add docstrings later.