Fixes EMNIST split and label issues (#2673)

* Add float support to ColorJitter

* Fix byclass EMNIST

* Fix bymerge, balance, letters EMNIST

* Fix whitespace indent

* Revert unrelated file changes

* Revert unrelated file changes

* Removing unnecessary type conversions.

* Removing the transform and adding dummy class instead.
Co-authored-by: Vasileios Vryniotis <vvryniotis@fb.com>

torchvision/datasets/mnist.py

@@ -249,13 +249,13 @@ class EMNIST(MNIST):
     md5 = "58c8d27c78d21e728a6bc7b3cc06412e"
     splits = ('byclass', 'bymerge', 'balanced', 'letters', 'digits', 'mnist')
     # Merged Classes assumes Same structure for both uppercase and lowercase version
-    _merged_classes = set(['C', 'I', 'J', 'K', 'L', 'M', 'O', 'P', 'S', 'U', 'V', 'W', 'X', 'Y', 'Z'])
-    _all_classes = set(list(string.digits + string.ascii_letters))
+    _merged_classes = {'c', 'i', 'j', 'k', 'l', 'm', 'o', 'p', 's', 'u', 'v', 'w', 'x', 'y', 'z'}
+    _all_classes = set(string.digits + string.ascii_letters)
     classes_split_dict = {
-        'byclass': list(_all_classes),
+        'byclass': sorted(list(_all_classes)),
         'bymerge': sorted(list(_all_classes - _merged_classes)),
         'balanced': sorted(list(_all_classes - _merged_classes)),
-        'letters': list(string.ascii_lowercase),
+        'letters': ['N/A'] + list(string.ascii_lowercase),
         'digits': list(string.digits),
         'mnist': list(string.digits),
     }