title: Merge Pandas Dataframes based on substring or partial match in another Dataframe
body: <p>I have two sample data frames:</p>
  <pre><code>df1 = pd.DataFrame({'Model': ['0RW52HC5KDD13R', '0RW52HC5KDD13U','JJS42HC5JSSAYR']})
  
  df2 = pd.DataFrame({'Group_Var': ['0RW52HC5K', '0RW52HC5K','JJS42HC5J']})
  </code></pre>
  <p>Using this will result result in an empty dataframe.</p>
  <pre><code>df3 = df1.merge(df2, left_on='Model', right_on='Group_Var')
  </code></pre>
  <p>How could I go about using a merge to use a substring / partial match from <code>df2['Group_Var']</code> in <code>df1['Model']</code>? Perhaps using the <code>str.contains()</code> method as part of the merge?</p>
  <p>Just for context my expected output would be something like this:</p>
  <pre><code>Group_Var        Model
  0RW52HC5K        0RW52HC5KDD13R
  0RW52HC5K        0RW52HC5KDD13U
  JJS42HC5J        JJS42HC5JSSAYR
  </code></pre>