title: use a dataframe column value as column name
body: <p>I meet a problem.I has a dataframe as below:</p>
  
  <pre><code>                  test_index test-item test_value
  Serial_Number                                 
  SN_0                    1         A      A-0.1
  SN_0                    1         B      B-0.1
  SN_0                    2         A      A-0.2
  SN_0                    2         B      B-0.2
  SN_1                    3         A      A-0.3
  SN_1                    3         B      B-0.3
  SN_1                    4         A      A-0.4
  SN_1                    4         B      B-0.4
  SN_3                    5         A      A-0.5
  SN_3                    5         B      B-0.5
  SN_3                    6         A      A-0.6
  SN_3                    6         B      B-0.6
  </code></pre>
  
  <p>I want get a dataframe like below:</p>
  
  <pre><code>Serial_Number       test_index             A           B              
  SN_0                    1               A-0.1       B-0.1
  SN_0                    2               A-0.2       B-0.2
  SN_1                    3               A-0.3       B-0.3
  SN_1                    4               A-0.4       B-0.4
  SN_3                    5               A-0.5       B-0.5
  SN_3                    6               A-0.6       B-0.6
  </code></pre>
  
  <p>i tried with <code>dataframe.unstack()</code>, <code>dataframe.reset_index()</code>,but i fail.</p>