'ManyRelatedManager' object is not iterable

When I'm writing an app ,in fact it's just a test.following is the actually code:
{% if query%}
{%for book in results%}

{{book.title}}


{%for author in book.authors%}

{{author.first_name}}|{{author.last_name}}

{%endfor%}

{{book.publisher.name}}

{%endfor%}
{%else%}

No Books Found

{%endif%}

When I run it.I got an error message:
'ManyRelatedManager' object is not iterable.

the solution for this is

change the for loop syntax to:

{%for author in book.authors.all%}

then it'll be done.