code: function parseClassHeader(idx, content) {
    let i = idx;
    i += 'class'.length;
    i = skip(i, content, c => {
      return isSpace(c);
    });
    // Skip all non space and non '<' characters
    let j = skip(i, content, c => {
      return !isSpace(c) && c !== '<';
    });
    const className = content.slice(i, j);
    i = j;
    // Skip spaces
    i = skip(i, content, c => {
      return isSpace(c);
    });
    if (content[i] === '<') {
      i += 1;
    } else {
      return null;
    } // Skip spaces
    i = skip(i, content, c => {
      return isSpace(c);
    });
    // Skip non-spaces
    j = skip(i, content, c => {
      return !isSpace(c);
    });
    if (content.slice(i, j) !== 'Formula') {
      return null;
    }
    return className;
  }
docs: /* This function parses the "class className < Formula" header
  and returns the className and index of the character just after the header