The function applies the rule to input words that are composed of two words, both starting with a capital letter. The rule does not hold for inputs that do not meet this criterion (either one-word inputs, two or more words with lowercase letters, or inputs with special characters), and the function simply returns 'undefined' for them.

To test the remaining 2 inputs, please provide them in the following format: COMMAND: PYTHON(./temp0/function.py "input1" "input2"). Replace "input1" and "input2" with the words you want to test.