'Give the string expression of a dimension in term of the basis symbols.'

def print_dim_base(self, dim):

    dims = self.dim_vector(dim)
    symbols = [(i.symbol if (i.symbol is not None) else i.name) for i in self._base_dims]
    res = S.One
    for (s, p) in zip(symbols, dims):
        res *= (s ** p)
    return res
