'Query or modify the heading options for the specified column.
If kw is not given, returns a dict of the heading option values. If
option is specified then the value for that option is returned.
Otherwise, sets the options to the corresponding values.
Valid options/values are:
text: text
The text to display in the column heading
image: image_name
Specifies an image to display to the right of the column
heading
anchor: anchor
Specifies how the heading text should be aligned. One of
the standard Tk anchor values
command: callback
A callback to be invoked when the heading label is
pressed.
To configure the tree column heading, call this with column = "#0"'

def heading(self, column, option=None, **kw):

    cmd = kw.get('command')
    if (cmd and (not isinstance(cmd, basestring))):
        kw['command'] = self.master.register(cmd, self._substitute)
    if (option is not None):
        kw[option] = None
    return _val_or_dict(kw, self.tk.call, self._w, 'heading', column)
