Function numpy::einsum_impl

pub fn einsum_impl<'py, T, DOUT>(
    subscripts: &str, 
    arrays: &[&'py PyArray<T, IxDyn>]
) -> PyResult<&'py PyArray<T, DOUT>> where
    DOUT: Dimension,
    T: Element, 

Return the Einstein summation convention of given tensors.

We also provide the einsum macro.