title: Model Output `to_excel` in Python?
body: <p>Running a MixedLM and want to push the output to Excel or a CSV, see model code and output below:</p>
  
  <pre><code>model = smf.mixedlm('y_var ~ gas_prices', dfModel, 
                   groups = dfModel['region'])
  mdf = model.fit()
  print(mdf.summary())
  
                  Mixed Linear Model Regression Results
  ======================================================================
  Model:                MixedLM   Dependent Variable:   yVar 
  No. Observations:     420       Method:               REML            
  No. Groups:           4         Scale:                45635645671.2271
  Min. group size:      105       Likelihood:           -5720.8133      
  Max. group size:      105       Converged:            Yes             
  Mean group size:      105.0                                           
  ----------------------------------------------------------------------
                Coef.     Std.Err.    z    P&gt;|z|    [0.025      0.975]  
  ----------------------------------------------------------------------
  Intercept  3241461.947 112718.823 28.757 0.000 3020537.112 3462386.781
  gas_prices -118128.471  46931.809 -2.517 0.012 -210113.126  -26143.816
  xVar2          275.017    165.072  1.666 0.096     -48.518     598.553
  groups RE        0.002                                                
  ======================================================================
  </code></pre>
  
  <p>I've tried pushing <code>mdf.summary().to_excel</code> and that didn't work, in addition to creating a Pandas DataFrame with <code>mdf.summary()</code> and then pushing to Excel, that doesn't work either.</p>
  
  <p>The extra credit piece here would be to create a unique filename for each output in Excel, so that if I run a few models they won't overwrite each other.</p>
  
  <p>How can I get this to Excel?</p>