Where does onClicked() and onCellClicked() come from?

[John Wong]

In this tutorial, Introduction to Pyjamas, Part 1  (http://goo.gl/wNFZb),
the write has this snippet

    def onCellClicked(self, sender, row, cell):
        self.gui_eventContactGridClicked(row, cell)

    def onClick(self, sender):
        if sender == self.addButton:
            self.gui_eventAddButtonClicked()
        elif sender == self.addNewButton:
            self.gui_eventAddNewButtonClicked()
        elif sender == self.updateButton:
            self.gui_eventUpdateButtonClicked()


I don't understand how onCellClicked() and onClick() get called. Are those
built-in methods of some GUI.ui.xxx class? I see multiple onClick() methods
from the documentation (http://pyjs.org/api/identifier-index.html), and
onCellClicked() under the Calendar (
http://pyjs.org/api/pyjamas.ui.Calendar.Calendar-class.html#onCellClicked)

I don't see where the inheritance is coming from. It is unclear to me.

For the full script, you may see it here:  http://pastebin.com/BRR9EJJS

Thank you. Please someone explain this to me, and advise me the best way to
pick up the APIs.

--
John