code: def _build_option_description(k):
      
  
      o = _get_registered_option(k)
      d = _get_deprecated_option(k)
  
      s = '{k} '.format(k=k)
  
      if o.doc:
          s += '\n'.join(o.doc.strip().split('\n'))
      else:
          s += 'No description available.'
  
      if o:
          s += ('\n    [default: {default}] [currently: {current}]'
                .format(default=o.defval, current=_get_option(k, True)))
  
      if d:
          s += '\n    (Deprecated'
          s += (', use `{rkey}` instead.'
                .format(rkey=d.rkey if d.rkey else ''))
          s += ')'
  
      return s
docs: Builds a formatted description of a registered option and prints it