def package_relpath(self, package_index):
ret = '<STR_LIT>'.format(package_index)<EOL>return ret<EOL>
Returns the relative path of the package

        This method returns the path to the package relative to the
        top dir of the working area. This method simply constructs the
        path based on the convention and doesn't check if the package
        actually exists.

        Parameters
        ----------
        package_index :
            a package index

        Returns
        -------
        str
            the relative path to the package