docs: def nanopub_validate(ctx, input_fn, output_fn, api, config_fn):
      """Validate nanopubs"""
  
      if config_fn:
          config = bel.db.Config.merge_config(ctx.config, override_config_fn=config_fn)
      else:
          config = ctx.config
  
      api = utils.first_true(
          [api, config["bel_api"]["servers"].get("api_url", None)], None
      )
  
      print(f"Running validate nanopubs using {api}")