Updates the text on the accept button, to reflect if the 
        name of the data file will result in opening an existing file,
        or creating a new one

def update_label(self):
        """Updates the text on the accept button, to reflect if the 
        name of the data file will result in opening an existing file,
        or creating a new one"""
        current_file = str(self.selectedFiles()[0])
        if not '.' in current_file.split(os.path.sep)[-1]:
            # add hdf5 extention if none given
            current_file += '.hdf5'
        if os.path.isfile(current_file):
            self.setLabelText(QtGui.QFileDialog.Accept, 'Reload')
        elif os.path.isdir(current_file):
            self.setLabelText(QtGui.QFileDialog.Accept, 'Open')
        else:
            self.setLabelText(QtGui.QFileDialog.Accept, 'Create')