title: Count specific value in pandas rolling window
body: <p>I have a dataframe with thousands rows. One column consists of only 3 values: -1, 0, 1. I would like to count in rolling window (let's say 100) how many times a specific value (let's say 0) occurs. </p>
  
  <p>How can I do it? I do not see such a method related to the object Rolling and I don't know how to do it by apply.</p>