An event is a simple JSON object (or python dict) with the following structure:
{
'run': int,
'event': int,
'lumi': int,
'event_type': string,
'data_time': string,
'dataset': string,
'vertex': {'position': [float, float, float]},
'electrons': [
{'pt' float, 'eta': float, 'phi': float, 'charge': int},
],
'muons': [
{'pt': float, 'eta': float, 'phi': float', 'charge': int},
],
'photons': [
{'energy': float, 'eta': float, 'phi': float},
],
'jets': [
{'energy': float, 'eta': float, 'phi': float}
],
'MET': {'et': float, 'phi': float}
}