How to use the pymoca.ast function in pymoca

def get_integer(self, tree: Union[ast.Primary, ast.ComponentRef, ast.Expression, ast.Slice]) -> Union[int, ca.MX, np.ndarray]:
        # CasADi needs to know the dimensions of symbols at instantiation.
        # We therefore need a mechanism to evaluate expressions that define dimensions of symbols.
        if isinstance(tree, ast.Primary):
            return None if tree.value is None else int(tree.value)
        if isinstance(tree, ast.ComponentRef):
            s = self.current_class.symbols[tree.name]
            assert (s.type.name == 'Integer')
            return self.get_integer(s.value)
        if isinstance(tree, ast.Expression):
            # Make sure that the expression has been converted to MX by (re)visiting the
            # relevant part of the AST.
            ast_walker = TreeWalker()
            ast_walker.walk(self, tree)

            # Obtain expression
            expr = self.get_mx(tree)

            # Obtain the symbols it depends on
            free_vars = ca.symvar(expr)

def get_integer(self, tree: Union[ast.Primary, ast.ComponentRef, ast.Expression, ast.Slice]) -> Union[int, ca.MX, np.ndarray]:
        # CasADi needs to know the dimensions of symbols at instantiation.
        # We therefore need a mechanism to evaluate expressions that define dimensions of symbols.
        if isinstance(tree, ast.Primary):
            return None if tree.value is None else int(tree.value)
        if isinstance(tree, ast.ComponentRef):
            s = self.current_class.symbols[tree.name]
            assert (s.type.name == 'Integer')
            return self.get_integer(s.value)
        if isinstance(tree, ast.Expression):
            # Make sure that the expression has been converted to MX by (re)visiting the
            # relevant part of the AST.
            ast_walker = TreeWalker()
            ast_walker.walk(self, tree)

            # Obtain expression
            expr = self.get_mx(tree)

            # Obtain the symbols it depends on
            free_vars = ca.symvar(expr)

            # Find the values of the symbols