title: How to remove dictionary's keys and values based on another dictionary?
body: <p>I wish to remove keys and values in one JSON dictionary based on another JSON dictionary's keys and values. In a sense I am looking perform a "subtraction". Let's say I have JSON dictionaries <code>a</code> and <code>b</code>:</p>
  
  <pre><code>a =  {
       "my_app":
          {
          "environment_variables":
             {
              "SOME_ENV_VAR":
                  [
                  "/tmp",
                  "tmp2"
                  ]
             },
  
          "variables":
             { "my_var": "1",
               "my_other_var": "2"
             }
          }
       }
  
  b =  {
        "my_app":
          {
          "environment_variables":
             {
              "SOME_ENV_VAR":
                  [
                  "/tmp"
                  ]
             },
  
          "variables":
             { "my_var": "1" }
          }
       }
  </code></pre>
  
  <p>Imagine you could do <code>a</code>-<code>b</code>=<code>c</code> where <code>c</code> looks like this:</p>
  
  <pre><code>c =  {
         "my_app":
         {
          "environment_variables":
             {
              "SOME_ENV_VAR":
                  [
                  "/tmp2"
                  ]
             },
  
          "variables":
             { "my_other_var": "2" }
         }
       }
  </code></pre>
  
  <p>How can this be done?</p>