Read the fusion extract

You will write three small functions that read the results of the tests on a sodium fusion extract. The results are stored in a dictionary. A test that was done and positive is True.

The idea. Nitrogen shows as Prussian blue or as the blood red colour of thiocyanate. Sulphur shows as the violet nitroprusside colour, as a black lead sulphide precipitate, or as thiocyanate. A halogen shows as a silver halide with a colour that names it.

Your tasks.

1. Complete has_nitrogen(r). It returns True when Prussian blue or the blood red colour is positive.
2. Complete has_sulphur(r). It returns True when the violet colour, the black precipitate or the blood red colour is positive.
3. Complete halogen(r). It looks up the colour of the silver halide in the table HALOGEN and returns the name, or None if there was no precipitate.