'Check if this file path refers to a regular file.
@return: C{True} if this L{FilePath} points to a regular file (not a
directory, socket, named pipe, etc), C{False} otherwise.
@rtype: L{bool}'

def isfile(self):

    st = self._statinfo
    if (not st):
        self.restat(False)
        st = self._statinfo
        if (not st):
            return False
    return S_ISREG(st.st_mode)
