This function links the user's choice of transformation with its inverse

def itransform_define(transform):
        """
        This function links the user's choice of transformation with its inverse
        """
        if transform == 'tanh':
            return np.arctanh
        elif transform == 'exp':
            return np.log
        elif transform == 'logit':
            return Family.logit
        elif transform is None:
            return np.array
        else:
            return None