code: def is_storage(self):
          
          if self.location == 'memory':
              return False
          # Use by slithIR SSA
          if self.location == 'reference_to_storage':
              return False
          if self.location == 'storage':
              return True
  
          if isinstance(self.type, (ArrayType, MappingType)):
              return True
  
          if isinstance(self.type, UserDefinedType):
              return isinstance(self.type.type, Structure)
  
          return False
docs: Return true if the variable is located in storage
              See https://solidity.readthedocs.io/en/v0.4.24/types.html?highlight=storage%20location#data-location
          Returns:
              (bool)