title: Preserving indentation in a triple-quoted fstring
body: <p>I am trying to use a triple-quoted strings in Python3(.7) to build some formated strings.</p>
  
  <p>I have a list of inner strings, which all need to be tabbed in:</p>
  
  <pre><code>    This is some text
      across multiple
      lines.
  </code></pre>
  
  <p>And a string which should contain the inner string</p>
  
  <pre><code>data{
      // string goes here
  }
  </code></pre>
  
  <p>I cannot tab the inner string when I create it. So, my thought was to use <code>dedent</code> with Python3 triple-quoted fstrings:</p>
  
  <pre><code>import textwrap
  
  inner_str = textwrap.dedent(
      '''\
      This is some text
      across multiple
      lines.'''
  )
  
  full_str = textwrap.dedent(
      f'''\
      data{{
          // This should all be tabbed
          {inner_str}
      }}'''
  )
  
  print(full_str)
  </code></pre>
  
  <p>However, the indentation is not maintained:</p>
  
  <pre><code>    data{
          // This should all be tabbed
          This is some text
  across multiple
  lines.
      }
  </code></pre>
  
  <p>The desired result:</p>
  
  <pre><code>data{
      // This should all be tabbed
      This is some text
      across multiple
      lines.
  }
  </code></pre>
  
  <p>How can I preserve the indentation of the fstring without pre-tabbing the inner string?</p>