fixing the loss syntax for l02c01

[bitekas]

Replacing the magic string constant with the canonical class name.
The previous format would cause incorrect code to compile but fail at runtime. The updated version checks the syntax on the compilation phase.
The exact class string code is an implementation detail and may change in the future making the example invalid.

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[bitekas]

@googlebot I signed it!

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[bitekas]

@googlebot I fixed it.