'Adds a tool tip. If a tooltip with the same name already exists, it updates it instead of adding a new one.
:param x: The x coordinate of the tip, in data coordinates.
:type x: float
:param y: The y coordinate of the tip, in data coordinates.
:type y: float
:param text: The text to show in the tip.
:type text: str or int
:param customX: The maximum horizontal distance in pixels from the point (x,y) at which to show the tooltip.
:type customX: float
:param customY: The maximum vertical distance in pixels from the point (x,y) at which to show the tooltip.
:type customY: float
If ``customX`` and ``customY`` are omitted, a default of 6 pixels is used.'

def addToolTip(self, x, y, text, customX=0, customY=0):

    self.positions.append((x, y, customX, customY))
    self.texts.append(text)
