code: def rsa_init(spec):
      
  
      try:
          size = spec['size']
      except KeyError:
          size = 2048
  
      kb = KeyBundle(keytype="RSA")
      if 'use' in spec:
          for use in harmonize_usage(spec["use"]):
              _key = new_rsa_key(use=use, key_size=size)
              kb.append(_key)
      else:
          _key = new_rsa_key(key_size=size)
          kb.append(_key)
  
      return kb
docs: Initiates a :py:class:`oidcmsg.keybundle.KeyBundle` instance
      containing newly minted RSA keys according to a spec.
      
      Example of specification::
          {'size':2048, 'use': ['enc', 'sig'] }
           
      Using the spec above 2 RSA keys would be minted, one for 
      encryption and one for signing.
          
      :param spec:
      :return: KeyBundle