call_sr: Internal function 'call_sr'
In IOR-Bioinformatics/PCSF: Network-based interpretation of highthroughput data

This function is internally used to solve the PCST.

1	call_sr(from, to, cost, node_names, node_prizes)

`from`	A `CharacterVector` that corresponds to `head` nodes of the edges.
`to`	A `CharacterVector` that corresponds the `tail` nodes of the edges.
`cost`	A `NumericVector` which represents the edge weights.
`node_names`	A `CharacterVector` demonstrates the names of the nodes.
`node_prizes`	A `NumericVector` which corresponds to the node prizes.