def getdarkcurrent(self,chip):
        """
        Return the dark current for the WFC3 UVIS detector.  This value
        will be contained within an instrument specific keyword.

        Returns
        -------
        darkcurrent: float
            The dark current value with **units of electrons**.
        """
        darkcurrent = 0.

        try:
            darkcurrent = self._image[self.scienceExt, chip].header['MEANDARK']

        except:
            msg =  "#############################################\n"
            msg += "#                                           #\n"
            msg += "# Error:                                    #\n"
            msg += "#   Cannot find the value for 'MEANDARK'    #\n"
            msg += "#   in the image header.  WFC3 input images #\n"
            msg += "#   are expected to have this header        #\n"
            msg += "#   keyword.                                #\n"
            msg += "#                                           #\n"
            msg += "# Error occured in WFC3UVISInputImage class #\n"
            msg += "#                                           #\n"
            msg += "#############################################\n"
            raise ValueError(msg)

        return darkcurrent
Return the dark current for the WFC3 UVIS detector.  This value
        will be contained within an instrument specific keyword.

        Returns
        -------
        darkcurrent: float
            The dark current value with **units of electrons**.