ef METHOD_NAME( self, rhs, func ):
  """Check to see if frames are the same.
  = ERROR CONDITIONS
  - If the frame of the rhs Duration is not the same as our frame,
    an error is thrown.
  = INPUT VARIABLES
  - rhs    The Duration to check for the same frame
  - func   The name of the function doing the check.
  """
  if self._frame != rhs._frame:
     msg = "Cannot %s Duration's with different frames.\n" \
           "LHS: %s\n" \
           "RHS: %s" % ( func, self._frame, rhs._frame )
     raise ValueError( msg )