def create_edge(_source, _target, _label='', _edge_type=''):
    """Creates an edge whose id is "source_target".

    Parameters:
    _source (str): source node @id
    _target (str): target node @id
    _label (str): label shown in graph
    _edge_type (str): type of edge, influences shape on graph
    
    """
    return {
        'data': {
            'id': f"{_source}__{_target}",
            '_label': f"\n\u2060{_label}\n\u2060",
            'name': _label,
            'source': _source,
            'target': _target,
            '_edge_type': _edge_type
        },
        'classes': ''
    }