###
3.1.5 PKey objects

The PKey object has the following methods:

`bits`()
  Return the number of bits of the key.

`generate_key`(type, bits)
  Generate a public/private key pair of the type type (one of `TYPE_RSA` and `TYPE_DSA`) with the size bits.

`type`()
  Return the type of the key.

`check`()
  Check the consistency of this key, returning True if it is consistent and raising an exception otherwise. This is only valid for RSA keys. See the OpenSSL RSA_check_key man page for further limitations.