DOC: Add isupper examples (#22285)

* added examples for isupper

* fixed examples for isupper

* Update numpy/core/defchararray.py

Co-authored-by: Rohit Goswami <r95g10@gmail.com>

* Update numpy/core/defchararray.py

Co-authored-by: Rohit Goswami <r95g10@gmail.com>

* Update numpy/core/defchararray.py

Co-authored-by: Rohit Goswami <r95g10@gmail.com>

* Update numpy/core/defchararray.py

Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>

Co-authored-by: Rohit Goswami <r95g10@gmail.com>
Co-authored-by: Sebastian Berg <sebastian@sipsolutions.net>
Co-authored-by: Ross Barnowski <rossbar@berkeley.edu>
Co-authored-by: Charles Harris <charlesr.harris@gmail.com>

numpy/core/defchararray.py

@@ -951,7 +951,7 @@ def istitle(a):
 @array_function_dispatch(_unary_op_dispatcher)
 def isupper(a):
     """
-    Returns true for each element if all cased characters in the
+    Return true for each element if all cased characters in the
     string are uppercase and there is at least one character, false
     otherwise.
 
@@ -976,7 +976,10 @@ def isupper(a):
     --------
     >>> str = "GHC"
     >>> np.char.isupper(str)
-    array(True) 
+    array(True)     
+    >>> a = np.array(["hello", "HELLO", "Hello"])
+    >>> np.char.isupper(a)
+    array([False,  True, False]) 
 
     """
     return _vec_string(a, bool_, 'isupper')