@staticmethod
def _io_map_span_node(source_name, line_number):
    """
        Create an empty span node containing source name and line number as
        attributes.  This is used to attach source info to an AST location,
        and then track that location through AST transformations and
        conversions.
        """
    span_node = {'t': 'Span', 'c': [['', ['codebraid--temp'], [['trace',
        '{0}:{1}'.format(source_name, line_number)]]], []]}
    return span_node
