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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _first_expander(fringe, iteration, viewer):
    '''
    Expander that expands only the first node on the fringe.
    '''
    current = fringe[0]
    neighbors = current.expand(local_search=True)

    if viewer:
        viewer.event('expanded', [current], [neighbors])

    fringe.extend(neighbors)