ValueError: Could not interpret input 'index' when using index with seaborn lineplot : <p>I want the use the index of a pandas DataFrame as x value for seaborn and is raised a value error.
A small test example:</p>

<pre><code>import pandas as pd
import seaborn as sns
sns.lineplot(x='index',y='test',hue='test2',data=pd.DataFrame({'test':range(9),'test2':range(9)}))
</code></pre>

<p>It raises:</p>

<pre><code>ValueError: Could not interpret input 'index'
</code></pre>

<p>is it not possible to use the index as x values? What am I doing wrong?
Python 2.7, seaborn 0.9</p>
