code: def split_conditional (property):
      
      assert isinstance(property, basestring)
      m = __re_split_conditional.match (property)
  
      if m:
          return (m.group (1), '<' + m.group (2))
  
      return None
docs: If 'property' is conditional property, returns
          condition and the property, e.g
          <variant>debug,<toolset>gcc:<inlining>full will become
          <variant>debug,<toolset>gcc <inlining>full.
          Otherwise, returns empty string.