sp-api-proc-macro is a procedural macro. It will run at compile time and transform your program's source code.
Adding sp-api-proc-macro macro(s) as a dependency
Run this command in a terminal, in your project's directory:
cargo add sp-api-proc-macro
To add it manually, edit your project's Cargo.toml file and add to the [dependencies] section:
sp-api-proc-macro = "26.0.0"
You may need to import the macro(s) with use sp_api_proc_macro::*.
sp_api_proc_macro documentation.