Creates a clamping from tuples of the form (variable, sign)

        Parameters
        ----------
        tuples : iterable[(str,int)]
            An iterable of tuples describing clamped variables

        Returns
        -------
        caspo.core.clamping.Clamping
            Created object instance

def from_tuples(cls, tuples):
        """
        Creates a clamping from tuples of the form (variable, sign)

        Parameters
        ----------
        tuples : iterable[(str,int)]
            An iterable of tuples describing clamped variables

        Returns
        -------
        caspo.core.clamping.Clamping
            Created object instance
        """
        return cls(it.imap(lambda (v, s): Literal(v, s), tuples))