get_content_type
Description:
Get the content type of the secret value, such as `text/plain`.
Parameters:
| this | 
           the value  | 
      
Returns:
| 
           the content type  | 
      
Get the content type of the secret value, such as `text/plain`.
| this | 
           the value  | 
      
| 
           the content type  |