/*!
* @fn upgmaTree
*
* @headerfile <seqan/graph_msa.h>
*
* @brief Computes a guide tree from a distance matrix.
*
* @signature void upgmaTree(mat, tree[, tag]);
*
* @param[in] mat A matrix with pairwise distance values. Can be a @link String
* @endlink representing a (dense) square matrix or a @link
* UndirectedGraph @endlink where each edge weight corresponds to
* the distance between sequence i and j (if the edge is
* present).
* @param[out] tree An undirected guide tre.
* @param[in] tag Tag indicating how to calcualte the cluster distances. See:
* @link UpgmaConfiguratorTags @endlink. Default:
* <tt>UpgmaWeightAvg</tt>.
*/