m1 = Matrix[[1,2,3],[4,5,6],[7,8,9]]
m2 = Matrix[[1,2,3],[4,5,6],[7,8]]

m1.row_size         #3
m1.column_size      #3
m2.row_size         #3
m2.column_size      #3      (misleading)
m1.square?          # true
m2.square?          # true (incorrect)

