Convert a PAC-learning algorithm into another one which requires no knowledge of the parameter

This is part of a problem in the book Foundations of Machine Learning(page 28). You can refer to chapter 2 for the notations. Consider a family of concept classes $\left\{\mathcal{C}_{s}\right\}_{s}$ where $\mathcal{C}_{s}$ is the set of concepts in $\mathcal{C}$ with size at most $s .$ Suppose we have a PAC-learning algorithm $\mathcal{A}$ that can be…

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why does not exist /dev in ubuntu-base-18.04.3-base-amd64.tar.gz?

/dev exists in ubuntu 18.04.1, 18.04.2. but /dev does not exist in ubuntu 18.04.3. Should I create /dev? get ubuntu-base. % curl -O http://cdimage.ubuntu.com/ubuntu-base/releases/18.04.3/release/ubuntu-base-18.04.1-base-amd64.tar.gz % curl -O http://cdimage.ubuntu.com/ubuntu-base/releases/18.04.3/release/ubuntu-base-18.04.2-base-amd64.tar.gz % curl -O http://cdimage.ubuntu.com/ubuntu-base/releases/18.04.3/release/ubuntu-base-18.04.3-base-amd64.tar.gz 18.04.1 % tar tzvf ubuntu-base-18.04.1-base-amd64.tar.gz | grep ” dev/” drwxr-xr-x root/root 0 2018-07-25 11:40 dev/ crw-rw-rw- root/root 1,8 2018-07-25 11:40 dev/random crw-rw-rw- root/root…

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