Import a private key from data in PEM-format

		:param pem_text: text with private key
		:param password: If it is not None, then result will be decrypt with the given password
		:return: None

def import_private_key(self, pem_text, password=None):
		""" Import a private key from data in PEM-format

		:param pem_text: text with private key
		:param password: If it is not None, then result will be decrypt with the given password
		:return: None
		"""
		if isinstance(pem_text, str) is True:
			pem_text = pem_text.encode()
		if password is not None and isinstance(password, str) is True:
			password = password.encode()

		self.__set_private_key(
			serialization.load_pem_private_key(pem_text, password=password, backend=default_backend())
		)