How to use the postcss.list.space function in postcss

return undefined;
    }

    var gridAreaRuleIndex = gridAreaMedia ? css.index(gridAreaMedia) : css.index(gridAreaRule);
    var value = gridArea.value; // found the data that matches grid-area identifier

    var data = gridTemplatesData.filter(function (d) {
      return d.allAreas.includes(value);
    })[0];

    if (!data) {
      return true;
    }

    var lastArea = data.allAreas[data.allAreas.length - 1];
    var selectorBySpace = list.space(gridAreaRule.selector);
    var selectorByComma = list.comma(gridAreaRule.selector);
    var selectorIsComplex = selectorBySpace.length > 1 && selectorBySpace.length > selectorByComma.length; // prevent doubling of prefixes

    if (hasPrefixedRow) {
      return false;
    } // create the empty object with the key as the last area name
    // e.g if we have templates with "a b c" values, "c" will be the last area


    if (!rulesToInsert[lastArea]) {
      rulesToInsert[lastArea] = {};
    } // walk through every grid-template rule data


    for (var _iterator2 = data.rules, _isArray2 = Array.isArray(_iterator2), _i2 = 0, _iterator2 = _isArray2 ? _iterator2 : _iterator2[Symbol.iterator]();;) {
      var _ref9;

if (_isArray3) {
          if (_i3 >= _iterator3.length) break;
          _ref10 = _iterator3[_i3++];
        } else {
          _i3 = _iterator3.next();
          if (_i3.done) break;
          _ref10 = _i3.value;
        }

        var tplSelector = _ref10;

        if (gridTemplateFound) {
          break;
        }

        var tplSelectorArr = list.space(tplSelector).filter(function (str) {
          return str !== '>';
        });
        gridTemplateFound = tplSelectorArr.every(function (item, idx) {
          return item === slicedSelectorArr[idx];
        });
      }

      if (gridTemplateFound || !hasArea) {
        return true;
      }

      if (!foundAreaSelector) {
        foundAreaSelector = parent.selector;
      } // if we found the duplicate area with different selector

function warnTemplateSelectorNotFound(decl, result) {
  var rule = decl.parent;
  var root = decl.root();
  var duplicatesFound = false; // slice selector array. Remove the last part (for comparison)

  var slicedSelectorArr = list.space(rule.selector).filter(function (str) {
    return str !== '>';
  }).slice(0, -1); // we need to compare only if selector is complex.
  // e.g '.grid-cell' is simple, but '.parent > .grid-cell' is complex

  if (slicedSelectorArr.length > 0) {
    var gridTemplateFound = false;
    var foundAreaSelector = null;
    root.walkDecls(/grid-template(-areas)?$/, function (d) {
      var parent = d.parent;
      var templateSelectors = parent.selectors;

      var _parseTemplate2 = parseTemplate({
        decl: d,
        gap: getGridGap(d)
      }),
          areas = _parseTemplate2.areas;

function warnTemplateSelectorNotFound (decl, result) {
  let rule = decl.parent
  let root = decl.root()
  let duplicatesFound = false

  // slice selector array. Remove the last part (for comparison)
  let slicedSelectorArr = list
    .space(rule.selector)
    .filter(str => str !== '>')
    .slice(0, -1)

  // we need to compare only if selector is complex.
  // e.g '.grid-cell' is simple, but '.parent > .grid-cell' is complex
  if (slicedSelectorArr.length > 0) {
    let gridTemplateFound = false
    let foundAreaSelector = null

    root.walkDecls(/grid-template(-areas)?$/, d => {
      let parent = d.parent
      let templateSelectors = parent.selectors

      let { areas } = parseTemplate({ decl: d, gap: getGridGap(d) })
      let hasArea = areas[decl.value]

.map(i => {
        return list.space(i).map(k => {
          return k.split(/(?=\.|#)/g)
        })
      })
  }

return list.comma(selector).map(function (i) {
      return list.space(i).map(function (k) {
        return k.split(/(?=\.|#)/g);
      });
    });
  }

replace (string, prefix) {
    return list.space(string)
      .map(value => {
        if (value.slice(0, +this.name.length + 1) !== this.name + '(') {
          return value
        }

        let close = value.lastIndexOf(')')
        let after = value.slice(close + 1)
        let args = value.slice(this.name.length + 1, close)

        if (prefix === '-webkit-') {
          let match = args.match(/\d*.?\d+%?/)
          if (match) {
            args = args.slice(match[0].length).trim()
            args += `, ${ match[0] }`
          } else {
            args += ', 0.5'

Flex.prototype.set = function set(decl, prefix) {
        var spec = flexSpec(prefix)[0];
        if (spec === 2009) {
            decl.value = list.space(decl.value)[0];
            decl.value = Flex.oldValues[decl.value] || decl.value;
            return _Declaration.prototype.set.call(this, decl, prefix);
        } else if (spec === 2012) {
            var components = list.space(decl.value);
            if (components.length === 3 && components[2] === '0') {
                decl.value = components.slice(0, 2).concat('0px').join(' ');
            }
        }
        return _Declaration.prototype.set.call(this, decl, prefix);
    };

_proto.set = function set(decl, prefix) {
    var spec = flexSpec(prefix)[0];

    if (spec === 2009) {
      decl.value = list.space(decl.value)[0];
      decl.value = Flex.oldValues[decl.value] || decl.value;
      return _Declaration.prototype.set.call(this, decl, prefix);
    }

    if (spec === 2012) {
      var components = list.space(decl.value);

      if (components.length === 3 && components[2] === '0') {
        decl.value = components.slice(0, 2).concat('0px').join(' ');
      }
    }

    return _Declaration.prototype.set.call(this, decl, prefix);
  };