Resolve "Slowdown due to arrays written as string in logger"

Changes to solve the issue #210 (closed).

Before merging

Before merging, please check the following items are fullfilled:

• All unit tests pass
• All modified and created methods/attributes are typed using typing.
• All methods input parameters and return parameters are described in the method docstring using numpydoc convention.
• There are no unused variables (including inwards or outwards).
• For each method, there is at least one unit test checking the expected default behaviour.

Closes #210 (closed)