title: import a schema but redefine a definition
body: <p>I want to import <a href="https://github.com/citation-style-language/schema/blob/master/schemas/input/csl-data.json" rel="nofollow noreferrer">this schema</a>, and redefine the following (simplified) definition so that its value is a string.</p>
  <pre><code>    &quot;date-variable&quot;: {
        &quot;properties&quot;: {
              &quot;date-parts&quot;: {
                &quot;type&quot;: &quot;array&quot;,
                &quot;items&quot;: {
                  &quot;type&quot;: &quot;array&quot;,
                  &quot;items&quot;: {
                    &quot;type&quot;: [&quot;string&quot;, &quot;number&quot;]
                  }
                }
              }
            }
          }
        }
  </code></pre>
  <p>Is that possible? If yes, how?</p>