title: Shortest way to replace values in nested JSON with the particular key elegantly
body: <p>Imagine a nested json structure as below: </p>
  
  <pre><code>node = 
  {
    "0" : {
      "param" : {
        "filename" : "abc",
        "delimiter" : "n"
      },
      "function" : "do something"
    },
    "1" : {
      "param" : {
        "filename" : "def",
        "delimiter" : "n"
      },
      "function" : "do something"
    },
    "2" : {
      "param" : {
        "filename" : "ghi",
        "delimiter" : "n"
      },
      "function" : "do something"
    }
  }
  </code></pre>
  
  <p>I wish to replace all the filename inside the node variable into computed filename. For example I want to replace all the values of filename in "0", "1", and "2" into "example.pdf".</p>
  
  <p>What is the most elegant way or shortest way to do so in Python?</p>