nptyping version downgrade to avoid code refactoring

[h2jaafar]

Currently, when new users pull the repository and create a venv, the requirements.txt file will install nptyping v2.0+, which seems to cause the following issue:

raise InvalidArgumentsError(
nptyping.error.InvalidArgumentsError: Unexpected argument '(typing.Any, typing.Any, typing.Any)', expecting Shape[<ShapeExpression>] or Literal[<ShapeExpression>] or typing.Any.

The syntax seems to have changed. This problem is dotted throughout the code.

A temporary fix is to simply peg the version of nptyping to 1.4.4, and avoid this problem at the moment.

[h2jaafar]

@uncobruce