def replace_node_field(reg, label, change):
    """ Call one of the field appropriate methods if we're changing just
    a field on a node. """
    if change['action'] == 'PUT' and change['field'] == '[text]':
        reg.replace_node_text(label, change)
    elif change['action'] == 'PUT' and change['field'] == '[title]':
        reg.replace_node_title(label, change)
    elif change['action'] == 'PUT' and change['field'] == '[heading]':
        reg.replace_node_heading(label, change)
