code: def _validate_isvalid_quantity(self, isvalid_quantity, field, value):
          
          quantity = Q_(value[0])
          low_lim = 0.0 * units(property_units[field])
  
          try:
              if quantity <= low_lim:
                  self._error(
                      field, 'value must be greater than 0.0 {}'.format(property_units[field]),
                  )
          except pint.DimensionalityError:
              self._error(field, 'incompatible units; should be consistent '
                          'with ' + property_units[field]
                          )
docs: Checks for valid given value and appropriate units.
  
          Args:
              isvalid_quantity (`bool`): flag from schema indicating quantity to be checked.
              field (`str`): property associated with quantity in question.
              value (`list`): list whose first element is a string representing a value with units
  
          The rule's arguments are validated against this schema:
              {'isvalid_quantity': {'type': 'bool'}, 'field': {'type': 'str'},
               'value': {'type': 'list'}}