Improve docstrings for get_fea_graph_point/get_magnetic_3d_graph_point

### 📝 Description of the feature

get_fea_graph_point/get_magnetic_3d_graph_point have lot's of index params. Some of these index from 0 and some index from 1. We should add some examples to clarify how these functions are used.

### 💡 Steps for implementing the feature

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### 🔗 Useful links and references

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