Cython / Sage: how to use Static Typing (cdef)?

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I'm looking at Sage developer guide for Cython: https://doc.sagemath.org/html/en/deve...

But I cannot find information about how to use static typing, which is what enables Cython (not necessarily in the context of Sage) to reach C-like performance. Since objects in Sage often have complicated types (expressions, polynomials), how would type declarations (cdef in Cython) work?

P.S. Does Cython have some type inference capability (like the "auto" keyword in C++) so the user can avoid typing long type names?