refactor string constants in DataModelWriter
refactor string constants in DataModelWriter

Senseg/robotframework,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,Senseg/robotframework,Senseg/robotframework,userzimmermann/robotframework-python3,userzimmermann/robotframework-python3,Senseg/robotframework,Senseg/robotframework