Return a function that will process `doc()` references in jinja, look
    them up in the manifest, and return the appropriate block contents.

def docs(node, manifest, config, column_name=None):
    """Return a function that will process `doc()` references in jinja, look
    them up in the manifest, and return the appropriate block contents.
    """
    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