def get_field_names(self, index=None):
return self.get_layout_objects(string_types, index=None, greedy=True)<EOL>
Returns a list of lists, those lists are named pointers. First parameter
is the location of the field, second one the name of the field. Example::

    [
        [[0,1,2], 'field_name1'],
        [[0,3], 'field_name2']
    ]