 pairwise metric strings (e.g. &quot;linear&quot;, &quot;rbf&quot;, &quot;laplacian&quot;,</span>
<span class="sd">                &quot;polynomial&quot;) or a custom callable. A callable should accept</span>
<span class="sd">                two arguments and the keyword arguments passed to this object</span>
<span class="sd">                as kernel_params, and should return a floating point number.</span>
<span class="sd">            gamma(float): Gamma parameter for the RBF, laplacian, polynomial,</span