made array_convert do isinstance instead of type comparison

metobs/data/__init__.py

@@ -313,7 +313,7 @@ def array_convert(arr, sunits, cunits):
     :type cunits: string
     """
     if sunits == cunits: return arr
-    if type(arr) != ndarray: raise ValueError("Array must be of type numpy.ndarray")
+    if not isinstance(arr, ndarray):: raise ValueError("Array must be of type numpy.ndarray, not %r" % (type(arr),))
     shape = arr.shape
     a = arr.flatten()
     if sunits == 'c':