chore: import upstream snapshot with attribution

easygraph/functions/basic/avg_degree.py

@@ -0,0 +1,31 @@
+__all__ = [
+    "average_degree",
+]
+
+
+def average_degree(G) -> float:
+    """Returns the average degree of the graph.
+
+    Parameters
+    ----------
+    G : graph
+        A EasyGraph graph
+
+    Returns
+    -------
+    average degree : float
+        The average degree of the graph.
+
+    Notes
+    -----
+    Self loops are counted twice in the total degree of a node.
+
+    Examples
+    --------
+    >>> G = eg.Graph()  # or DiGraph, MultiGraph, MultiDiGraph, etc
+    >>> G.add_edge(1, 2)
+    >>> G.add_edge(2, 3)
+    >>> eg.average_degree(G)
+    1.3333333333333333
+    """
+    return G.number_of_edges() / G.number_of_nodes() * 2