title: how to use extends_documentation_fragment. getting error while using it
body: <p>I am writing my own ansible modules which shares the same document across multiple modules which I need to develop.
  As per the ansible website <a href="https://docs.ansible.com/ansible/latest/dev_guide/developing_modules_documenting.html" rel="nofollow noreferrer">https://docs.ansible.com/ansible/latest/dev_guide/developing_modules_documenting.html</a> we can use extends_documentation_fragment.</p>
  
  <p>After going through the web link this is what i did on my centos (ansible controller)</p>
  
  <p>I create a new doc file (<code>alokdoc.py</code>) with below content.</p>
  
  <pre class="lang-py prettyprint-override"><code>class ModuleDocFragment(object):
  
      DOCUMENTATION = r'''
      array_ip:
        description:
        - "The storage system IP address."
        required: True
      array_password:
        description:
        - "The storage system password."
        required: True
      array_username:
        description:
        - "The storage system user name."
        required: True
      '''
  </code></pre>
  
  <p>I saved this under the following directory </p>
  
  <p><code>/usr/lib/python3.6/site-packages/ansible/plugins/doc_fragments</code> as <code>alokdoc.py</code></p>
  
  <p>Now in my ansible module, namely, <code>alok_module1.py</code>, located under <code>/etc/ansible/library/modules</code>, I wrote the below </p>
  
  <pre class="lang-py prettyprint-override"><code>- DOCUMENTATION = r'''
  ---
  author: "alok.ranjan@****.com"
  
  description: "my first module"
  
  module: alok_module1
  
  extends_documentation_fragment:
  
      - alokdoc
  
  .
  .
  .
  </code></pre>
  
  <p>Also, in my <code>ansible.cfg</code> file I have these two variables enabled .. </p>
  
  <pre><code>library        = /etc/ansible/library/modules
  
  module_utils = /usr/lib/python3.6/site-packages/ansible/module_utils
  </code></pre>
  
  <p>When I run the below command I get error </p>
  
  <pre><code>$ ansible-doc -t module "alok_module1.py"**
  
  ERROR! module alok_module1 missing documentation (or could not parse documentation): unknown doc_fragment(s) in file /etc/ansible/library/modules/alok_module1.py: alokdoc
  </code></pre>
  
  <p>Why am I getting this error. what am I missing??</p>
  
  <p>thanks</p>