Creates a graph from an iterable of tuples describing edges like (source, target, sign)

        Parameters
        ----------
        tuples : iterable[(str,str,int))]
            Tuples describing signed and directed edges

        Returns
        -------
        caspo.core.graph.Graph
            Created object instance

def from_tuples(cls, tuples):
        """
        Creates a graph from an iterable of tuples describing edges like (source, target, sign)

        Parameters
        ----------
        tuples : iterable[(str,str,int))]
            Tuples describing signed and directed edges

        Returns
        -------
        caspo.core.graph.Graph
            Created object instance
        """
        return cls(it.imap(lambda (source, target, sign): (source, target, {'sign': sign}), tuples))