##### SUMMARY
The documentation of the module *user* / parameter *shell* states:

https://github.com/ansible/ansible/blob/8edad83ae029d7838a6d6347576d2ddbcce12ad0/lib/ansible/modules/system/user.py#L79

But there are no (shell specific) notes.
##### ISSUE TYPE
- Documentation Report

##### COMPONENT NAME
user / docs

##### ANSIBLE VERSION
devel branch

##### CONFIGURATION
N/A

##### OS / ENVIRONMENT
N/A

##### ADDITIONAL INFORMATION
Either remove the sentence or provide some information in the notes section.

'''Convert SELF.GROUP to is stringed numerical value suitable for dscl.'''
        if self.group is None:
            self.group = 'nogroup'
        try:
            self.group = grp.getgrnam(self.group).gr_gid
        except KeyError:
            self.module.fail_json(msg='Group "%s" not found. Try to create it first using "group" module.' % self.group)
        
        self.group = str(self.group)
    def __modify_group(self, group, action):
        '''Add or remove SELF.NAME to or from GROUP depending on ACTION.
        ACTION can be 'add' or 'remove' otherwise 'remove' is assumed. '''
        if action == 'add':
            option = '-a'
        else:
            option = '-d'
        cmd = ['dseditgroup', '-o', 'edit', option, self.name, '-t', 'user', group]
        (rc, out, err) = self.execute_command(cmd)
        if rc != 0:
            self.module.fail_json(msg='Cannot %s user "%s" to group "%s".'
                                      % (action, self.name, group), err=err, out=out, rc=rc)
        return (rc, out, err)
    def _modify_group(self):