code: def variables(package):
      
      _raise_if_not_exists(package)
      result = _query(package, '--print-variables')
      names = (x.strip() for x in result.split('\n') if x != '')
      return dict(((x, _query(package, '--variable={0}'.format(x)).strip()) for x in names))
docs: Return a dictionary of all the variables defined in the .pc pkg-config file
      of 'package'.