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)

def is_storage(self):
        """
            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)
        """
        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