function _matrixNormOne (x) {
      // norm(x) = the largest column sum
      const c = []
      // result
      let maxc = 0
      // skip zeros since abs(0) == 0
      x.forEach(function (value, index) {
        const j = index[1]
        const cj = add(c[j] || 0, abs(value))
        if (larger(cj, maxc)) {
          maxc = cj
        }
        c[j] = cj
      }, true)
      return maxc
    }
Calculate the norm L1 for a matrix
@param {Matrix} x
@returns {number} Returns the norm
@private