code: def _clean_quantity(self, quantity):
          
          value = quantity.get(QUANTITY.VALUE, '').strip()
          error = quantity.get(QUANTITY.E_VALUE, '').strip()
          unit = quantity.get(QUANTITY.U_VALUE, '').strip()
          kind = quantity.get(QUANTITY.KIND, '')
  
          if isinstance(kind, list) and not isinstance(kind, string_types):
              kind = [x.strip() for x in kind]
          else:
              kind = kind.strip()
  
          if not value:
              return False
  
          if is_number(value):
              value = '%g' % Decimal(value)
          if error:
              error = '%g' % Decimal(error)
  
          if value:
              quantity[QUANTITY.VALUE] = value
          if error:
              quantity[QUANTITY.E_VALUE] = error
          if unit:
              quantity[QUANTITY.U_VALUE] = unit
          if kind:
              quantity[QUANTITY.KIND] = kind
  
          return True
docs: Clean quantity value before it is added to entry.