title: Convert dict to nested list, inserting keys into each sublist
body: <p>I have a solution to this question, but I'm curious if there might be a better way.
  I have a dict like this:</p>
  
  <pre><code>dict1 = {
  'key1':[['value1','value2','value3'],['value4','value5','value6']],
  'key2':[['value7','value8','value9'],['value10','value11','value12']],
  'key3':[['value13','value14','value15'],['value16','value17','value18']]}
  </code></pre>
  
  <p>I want to convert this into a nested list, and inserting the keys into the new sublist like this:</p>
  
  <pre><code>nestedlist = [
  ['value1','value2','key1','value3'],['value4','value5','key1','value6'],
  ['value7','value8','key1','value9'],['value10','value11','key2','value12'],
  ['value13','value14','key2','value15'],['value16','value17','key2','value18'],
  ['value10','value11','key3','value12'],['value13','value14','key3','value15'],
  ['value16','value17','key3','value18']]
  </code></pre>
  
  <p>I solve this the following way:</p>
  
  <pre><code>keys = [*dict1]
  newlist = []
  for item in keys:
      for item2 in dict1[item]:
          item2.insert(2,item)
          newlist.append(item2)
  </code></pre>
  
  <p>so, how can i improve this piece of code?</p>