[docs] Bugs in Python 3.7 documentation.

[Никита Люшненко]

https://docs.python.org/3/reference/datamodel.html#metaclass-example - 
    "uses an collections.OrderedDict to remember" when it is better to use "uses a collections.OrderedDict to remember"

https://docs.python.org/3/reference/executionmodel.html#exceptions
"Exceptions are a means" - Is it correct to use "a" here? "means" means a lot of them. "a" means one.

"In either case, it prints a stack backtrace" - most of the time in Python documentation term "traceback" is used instead of "backtrace". It may mislead newcomers, so they will think, that this is potentially a new term.

https://docs.python.org/3/reference/expressions.html#yield-expressions
"Due to their side effects on the containing scope, yield expressions are not permitted as part of the implicitly defined scopes used to implement comprehensions and generator expressions (in Python 3.7, such expressions emit DeprecationWarning when compiled, in Python 3.8+ they will emit SyntaxError).." - two periods in the end of the sentence.

https://docs.python.org/3/reference/expressions.html#yield-expressions
"...or automatically when the sub-iterator is a generator (by returning a value from the sub-generator)." - inconsistent use of "sub-iterator" term. Previously subiterator was referenced several times as "subiterator" not "sub-iterator".

If i understood something wrong, then i am sorry.

-- 
Sincerely,
ZooDSS
ZooDSS at yandex.ru