Removes edges in a graph, where both the source and the target of an edge is the same node.
For certain analyses, self loops may either not make sense, or it may be useful to ignore them. If one has a network of friends, being your own friend may not make much sense, and may need to be removed.
Also, if one had a network of the flow of goods produced by a country to other countries, one might have a self-loop for a country which was the recipient of its own goods. For some analyses, we might want to include this edge, but if we only wanted to consider exports it would be necessary to remove it.