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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 _list_nodes(call=None):
    '''
    List the nodes, ask all 'vagrant' minions, return dict of grains.
    '''
    local = salt.client.LocalClient()
    ret = local.cmd('salt-cloud:driver:vagrant', 'grains.items', '', tgt_type='grain')
    return ret