+ Boundary points lie in the cone as well:
+
+ >>> K = SymmetricPSD(2)
+ >>> matrix([[0,0],[0,0]]) in K
+ True
+
+ >>> K = SymmetricPSD(5)
+ >>> A = matrix([[1,0,0,0,0],
+ ... [0,1,0,0,0],
+ ... [0,0,0,0,0],
+ ... [0,0,0,1,0],
+ ... [0,0,0,0,1]])
+ >>> A in K
+ True
+
+ However, this matrix has a negative eigenvalue:
+
+ >>> K = SymmetricPSD(2)
+ >>> A = matrix([[ 1, -2],
+ ... [-2, 1]])
+ >>> A in K
+ False
+
+ An asymmetric cone with positive eigenvalues is not in the cone:
+
+ >>> K = SymmetricPSD(2)
+ >>> A = matrix([[10, 2],
+ ... [4, 8]])
+ >>> A in K
+ False
+
+ Junk arguments don't work:
+
+ >>> K = SymmetricPSD(2)
+ >>> [[1,2],[2,3]] in K