code: def add_role(ctx, role):
      
  
      if role is None:
          log('Specify the role with --role')
          return
      if ctx.obj['username'] is None:
          log('Specify the username with --username')
          return
  
      change_user = ctx.obj['db'].objectmodels['user'].find_one({
          'name': ctx.obj['username']
      })
      if role not in change_user.roles:
          change_user.roles.append(role)
          change_user.save()
          log('Done')
      else:
          log('User already has that role!', lvl=warn)
docs: Grant a role to an existing user