quickfix syntax / typo (nltk#3215)

* fix typo / syntax error

* refactor comparison to None

* format file with black to pass pre-commit checks

Author: purificant

nltk/chat/eliza.py

@@ -328,8 +328,10 @@ def eliza_chat():
 
     eliza_chatbot.converse()
 
+
 def demo():
     eliza_chat()
 
+
 if __name__ == "__main__":
     eliza_chat()

nltk/metrics/aline.py

@@ -1221,7 +1221,7 @@ def delta(p, q):
     """
     features = R(p, q)
     total = 0
-    if np != None:
+    if np is not None:
         return np.dot(
             [diff(p, q, f) for f in features], [salience[f] for f in features]
         )

nltk/metrics/confusionmatrix.py

@@ -197,7 +197,7 @@ def key(self):
         str = "Value key:\n"
         indexlen = len(repr(len(values) - 1))
         key_format = "  %" + repr(indexlen) + "d: %s\n"
-        str += str += "".join([key_format % (i, values[i]) for i in range(len(values))])
+        str += "".join([key_format % (i, values[i]) for i in range(len(values))])
         return str
 
     def recall(self, value):