Compute the degree centrality for nodes.
The degree centrality for a node v is the fraction of nodes it is connected to.
G : graph
A networkx graph
nodes : dictionary
Dictionary of nodes with degree centrality as the value.
The degree centrality values are normalized by dividing by the maximum possible degree in a simple graph n-1 where n is the number of nodes in G.
For multigraphs or graphs with self loops the maximum degree might be higher than n-1 and values of degree centrality greater than 1 are possible.