code: function validateCommaItemSpacing(previousItemToken, commaToken, currentItemToken, reportItem) {
  
              // if single line
              if (astUtils.isTokenOnSameLine(commaToken, currentItemToken) &&
                      astUtils.isTokenOnSameLine(previousItemToken, commaToken)) {
  
                  // do nothing.
  
              } else if (!astUtils.isTokenOnSameLine(commaToken, currentItemToken) &&
                      !astUtils.isTokenOnSameLine(previousItemToken, commaToken)) {
  
                  const comment = sourceCode.getCommentsAfter(commaToken)[0];
                  const styleType = comment && comment.type === "Block" && astUtils.isTokenOnSameLine(commaToken, comment)
                      ? style
                      : "between";
  
                  // lone comma
                  context.report({
                      node: reportItem,
                      loc: {
                          line: commaToken.loc.end.line,
                          column: commaToken.loc.start.column
                      },
                      messageId: "unexpectedLineBeforeAndAfterComma",
                      fix: getFixerFunction(styleType, previousItemToken, commaToken, currentItemToken)
                  });
  
              } else if (style === "first" && !astUtils.isTokenOnSameLine(commaToken, currentItemToken)) {
  
                  context.report({
                      node: reportItem,
                      messageId: "expectedCommaFirst",
                      fix: getFixerFunction(style, previousItemToken, commaToken, currentItemToken)
                  });
  
              } else if (style === "last" && astUtils.isTokenOnSameLine(commaToken, currentItemToken)) {
  
                  context.report({
                      node: reportItem,
                      loc: {
                          line: commaToken.loc.end.line,
                          column: commaToken.loc.end.column
                      },
                      messageId: "expectedCommaLast",
                      fix: getFixerFunction(style, previousItemToken, commaToken, currentItemToken)
                  });
              }
          }
docs: Validates the spacing around single items in lists.
  @param {Token} previousItemToken The last token from the previous item.
  @param {Token} commaToken The token representing the comma.
  @param {Token} currentItemToken The first token of the current item.
  @param {Token} reportItem The item to use when reporting an error.
  @returns {void}
  @private