Return the requested filenames.

        Parameters:
        -----------
        pixels : requeseted pixels

        Returns:
        --------
        filenames : recarray

def getFilenames(self,pixels=None):
        """
        Return the requested filenames.

        Parameters:
        -----------
        pixels : requeseted pixels

        Returns:
        --------
        filenames : recarray
        """
        logger.debug("Getting filenames...")
        if pixels is None:
            return self.filenames
        else:
            return self.filenames[np.in1d(self.filenames['pix'],pixels)]