Demonstrate the overwrite option to data exchange

dataexchange dataset overwrite

import dataexchange.xtomo.data_xchange as dex
import numpy as np

data = np.zeros((10,10))

f = dex.DataExchangeFile('text.h5', 'w')
# Create initial entry
f.add_entry( 
    DataExchangeEntry.data(
        root='/exchange_1',
        data={'value': data, 'units':'counts', 'description': 'transmission', 'axes':'theta:y:x' }
    )
)
# Overwrite initial entry
f.add_entry( 
    DataExchangeEntry.data(
        root='/exchange_1',
        data={'value': data, 'units':'counts', 'description': 'transmission', 'axes':'theta:y:x' }
    ), overwrite=True
)

# This will not overwrite
f.add_entry( 
    DataExchangeEntry.data(
        root='/exchange_1',
        data={'value': data, 'units':'counts', 'description': 'transmission', 'axes':'theta:y:x' }
    )
)