Compute the value (size) of each node by summing the associated links.

def computeNodeValues(cls, graph):
        """
        Compute the value (size) of each node by summing the associated links.
        """
        for node in graph['nodes']:
            source_val = np.sum([l['value'] for l in node['sourceLinks']])
            target_val = np.sum([l['value'] for l in node['targetLinks']])
            node['value'] = max([source_val, target_val])