code: function buildFunctionSignature (paramTypes, returnTypes, isPayable, additionalMods) {
    return 'function (' + util.concatWithSeperator(paramTypes, ',') + ')' + ((isPayable) ? ' payable' : '') + ((additionalMods) ? ' ' + additionalMods : '') + ((returnTypes.length) ? ' returns (' + util.concatWithSeperator(returnTypes, ',') + ')' : '')
  }
docs: Builds an function signature as used in the AST of the solc-json AST
  @param {Array} paramTypes
  list of parameter type names
  @param {Array} returnTypes
  list of return type names
  @return {Boolean} isPayable