Added docstring for square

unnecessarymath.py

@@ -8,12 +8,18 @@ def sqrt(x):
 
     >>> sqrt(4)
     2.0
-
     >>> sqrt(1.)
     1.0
     """
     return np.sqrt(x)
 
 def square(x):
-    """Evaluate the square of a number"""
+    """
+    Evaluate the square of a number
+
+    >>> square(2)
+    4
+    >>> square(4.)
+    16.
+    """
     return x * x