code: def docs(node, manifest, config, column_name=None):
      
      current_project = config.project_name
  
      def do_docs(*args):
          if len(args) == 1:
              doc_package_name = None
              doc_name = args[0]
          elif len(args) == 2:
              doc_package_name, doc_name = args
          else:
              dbt.exceptions.doc_invalid_args(node, args)
  
          target_doc = ParserUtils.resolve_doc(
              manifest, doc_name, doc_package_name, current_project,
              node.package_name
          )
  
          if target_doc is None:
              dbt.exceptions.doc_target_not_found(node, doc_name,
                                                  doc_package_name)
  
          return target_doc.block_contents
  
      return do_docs
docs: Return a function that will process `doc()` references in jinja, look
      them up in the manifest, and return the appropriate block contents.