How to use the xmlsec.cryptoAppDefaultKeysMngrInit function in xmlsec

def load_rsa_keys(key_file):
    assert(key_file)

    # Create and initialize keys manager, we use a simple list based
    # keys manager, implement your own KeysStore klass if you need
    # something more sophisticated
    mngr = xmlsec.KeysMngr()
    if mngr is None:
        print "Error: failed to create keys manager."
        return None
    if xmlsec.cryptoAppDefaultKeysMngrInit(mngr) < 0:
        print "Error: failed to initialize keys manager."
        mngr.destroy()
        return None
    # Load private RSA key
    if not check_filename(key_file):
        mngr.destroy()
        return None
    key = xmlsec.cryptoAppKeyLoad(key_file, xmlsec.KeyDataFormatPem,
                                  None, None, None);
    if key is None:
        print "Error: failed to load rsa key from file \"%s\"" % key_file
        mngr.destroy()
        return None
    # Set key name to the file name, this is just an example!
    if key.setName(key_file) < 0:
        print "Error: failed to set key name for key from \"%s\"" % key_file

xmlsec.DSigNs)
      if not node:
        raise SignatureError("couldn't find root node")

      # load the private key
      key = xmlsec.cryptoAppKeyLoad(self.key_file, xmlsec.KeyDataFormatPem,
                                    self.key_pwd, None, None)
      if not key:
        raise SignatureError('failed to load the private key %s' % self.key_file)

      if xmlsec.cryptoAppKeyCertLoad(key, self.cert_file, xmlsec.KeyDataFormatPem) < 0:
        print "Error: failed to load pem certificate \"%s\"" % self.cert_file
        return self.cleanup(doc, dsigctx)

      keymngr = xmlsec.KeysMngr()
      xmlsec.cryptoAppDefaultKeysMngrInit(keymngr)
      xmlsec.cryptoAppDefaultKeysMngrAdoptKey(keymngr, key)
      dsigctx = xmlsec.DSigCtx(keymngr)

      if key.setName(self.key_file) < 0:
        raise SignatureError('failed to set key name')

      # sign
      if dsigctx.sign(node) < 0:
        raise SignatureError('signing failed')
      signed_xml = doc.serialize()

    finally:
      if dsigctx:
        dsigctx.destroy()
      if doc:
        doc.freeDoc()

def load_trusted_certs(files, files_size):
    assert(files)
    assert(files_size > 0)

    # Create and initialize keys manager, we use a simple list based
    # keys manager, implement your own KeysStore klass if you need
    # something more sophisticated
    mngr = xmlsec.KeysMngr()
    if mngr is None:
        print "Error: failed to create keys manager."
        return None
    if xmlsec.cryptoAppDefaultKeysMngrInit(mngr) < 0:
        print "Error: failed to initialize keys manager."
        mngr.destroy()
        return None
    for file in files:
        if not check_filename(file):
            mngr.destroy()
            return None
        # Load trusted cert
        if mngr.certLoad(file, xmlsec.KeyDataFormatPem,
                         xmlsec.KeyDataTypeTrusted) < 0:
            print "Error: failed to load pem certificate from \"%s\"", file
            mngr.destroy()
            return None
    return mngr

def load_des_keys(files, files_size):
    assert(files)
    assert(files_size > 0)

    # Create and initialize keys manager, we use a simple list based
    # keys manager, implement your own KeysStore klass if you need
    # something more sophisticated
    mngr = xmlsec.KeysMngr()
    if mngr is None:
        print "Error: failed to create keys manager."
        return None
    if xmlsec.cryptoAppDefaultKeysMngrInit(mngr) < 0:
        print "Error: failed to initialize keys manager."
        mngr.destroy()
        return None
    for file in files:
        if not check_filename(file):
            mngr.destroy()
            return None
        # Load DES key
        key = xmlsec.keyReadBinaryFile(xmlsec.keyDataDesId(), file)
        if key is None:
    	    print "Error: failed to load des key from binary file \"%s\"" % file
	    mngr.destroy()
            return None
        # Add key to keys manager, from now on keys manager is responsible
	# for destroying key
        if xmlsec.cryptoAppDefaultKeysMngrAdoptKey(mngr, key) < 0:

def load_trusted_certs(files, files_size):
    assert(files)
    assert(files_size > 0)

    # Create and initialize keys manager, we use a simple list based
    # keys manager, implement your own KeysStore klass if you need
    # something more sophisticated
    mngr = xmlsec.KeysMngr()
    if mngr is None:
        print "Error: failed to create keys manager."
        return None
    if xmlsec.cryptoAppDefaultKeysMngrInit(mngr) < 0:
        print "Error: failed to initialize keys manager."
        mngr.destroy()
        return None
    for file in files:
        if not check_filename(file):
            mngr.destroy()
            return None
        # Load trusted cert
        if mngr.certLoad(file, xmlsec.KeyDataFormatPem,
                         xmlsec.KeyDataTypeTrusted) < 0:
            print "Error: failed to load pem certificate from \"%s\"", file
            mngr.destroy()
            return None
    return mngr

def load_keys(files, files_size):
    assert(files)
    assert(files_size > 0)

    # Create and initialize keys manager, we use a simple list based
    # keys manager, implement your own KeysStore klass if you need
    # something more sophisticated
    mngr = xmlsec.KeysMngr()
    if mngr is None:
        print "Error: failed to create keys manager."
        return None
    if xmlsec.cryptoAppDefaultKeysMngrInit(mngr) < 0:
        print "Error: failed to initialize keys manager."
        mngr.destroy()
        return None
    for file in files:
        # Load key
        if not check_filename(file):
            mngr.destroy()
            return None
        key = xmlsec.cryptoAppKeyLoad(file, xmlsec.KeyDataFormatPem,
                                      None, None, None)
        if key == None:
            print "Error: failed to load pem key from " + file
            mngr.destroy()        
            return None
        # Set key name to the file name, this is just an example!
        if key.setName(file) < 0: