code: def fileParameter(self, comp):
          
          for row in range(self.nrows()):
              p = self._parameters[row]
              if p['parameter'] == 'filename':
                  # ASSUMES COMPONENT IN ONE SELECTION
                  if comp in p['selection']:
                      return row
docs: Returns the row which component *comp* can be found in the 
          selections of, and is also a filename parameter
  
          :returns: int -- the index of the (filename) parameter *comp* is a member of