code: function pm(m) {
      if (m[4] === 0 && m[5] === 0) {
        if (m[1] === 0 && m[2] === 0) {
          if (m[0] === 1 && m[3] === 1) {
            return '';
          }
          return 'scale(' + pf(m[0]) + ' ' + pf(m[3]) + ')';
        }
        if (m[0] === m[3] && m[1] === -m[2]) {
          var a = Math.acos(m[0]) * 180 / Math.PI;
          return 'rotate(' + pf(a) + ')';
        }
      } else {
        if (m[0] === 1 && m[1] === 0 && m[2] === 0 && m[3] === 1) {
          return 'translate(' + pf(m[4]) + ' ' + pf(m[5]) + ')';
        }
      }
      return 'matrix(' + pf(m[0]) + ' ' + pf(m[1]) + ' ' + pf(m[2]) + ' ' +
        pf(m[3]) + ' ' + pf(m[4]) + ' ' + pf(m[5]) + ')';
    }
docs: Formats transform matrix. The standard rotation, scale and translate
  matrices are replaced by their shorter forms, and for identity matrix
  returns empty string to save the memory.
  @param m {Array} matrix to format.
  @returns {string}