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[W4.3a] Principles → Liskov substitution principle 
 
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[W4.3b] Principles → Open-closed principle 
 
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[W4.3c] Principles → Law of Demeter 
 
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[W4.3d] Principles → Interface segregation principle : OPTIONAL
 
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[W4.3e] Principles → Dependency inversion principle : OPTIONAL
 
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[W4.3f] Principles → SOLID principles