Lark parser Indenter class not working while using lark.visitors.Interpreter class

Question

So I'm making a programming language using the lark library in python, up until now, I was using the class Transformer(), but now I've switched to the lark.visitors.Interpreter() class. I've been copying over my progress from Transformer to Interpreter, but I cant seem to get the Indenter class working. For example, if I parse

5 + 5
5 + 5

When I parse this, I'm getting the following error:

PS E:\ParserAndLexer> & C:/Python38/python.exe e:/ParserAndLexer/lite/lite_interpreter.py
Traceback (most recent call last):
  File "C:\Python38\lib\site-packages\lark\parsers\lalr_parser.py", line 59, in get_action
    return states[state][token.type]
KeyError: 'NUMBER'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "e:/ParserAndLexer/lite/lite_interpreter.py", line 46, in <module>
    tree = parser.parse(lite_code)
  File "C:\Python38\lib\site-packages\lark\lark.py", line 464, in parse
    return self.parser.parse(text, start=start)
  File "C:\Python38\lib\site-packages\lark\parser_frontends.py", line 148, in parse
    return self._parse(token_stream, start, set_parser_state)
  File "C:\Python38\lib\site-packages\lark\parser_frontends.py", line 63, in _parse
    return self.parser.parse(input, start, *args)
  File "C:\Python38\lib\site-packages\lark\parsers\lalr_parser.py", line 35, in parse
    return self.parser.parse(*args)
  File "C:\Python38\lib\site-packages\lark\parsers\lalr_parser.py", line 88, in parse
    action, arg = get_action(token)
  File "C:\Python38\lib\site-packages\lark\parsers\lalr_parser.py", line 66, in get_action
    raise UnexpectedToken(token, expected, state=state, puppet=puppet)
lark.exceptions.UnexpectedToken: Unexpected token Token('NUMBER', '5') at line 2, column 1.
Expected one of:
        * __ANON_0
        * $END

My code looks somewhat like this:

from lark.visitors import Interpreter
from lark import Lark
from lark.indenter import Indenter

class MainIndenter(Indenter):
    NL_type = '_NL'
    OPEN_PAREN_types = ['LPAR', 'LBRACE']
    CLOSE_PAREN_types = ['RPAR', 'RBRACE']
    INDENT_TYPE = '_INDENT'
    DEDENT_type = '_DEDENT'
    tab_len = 8

class MainInterpreter(Interpreter):
    number = int
    string = str
    
    def __init__(self):
        self.vars = {}

    def add(self, tree):
        return int(tree.children[0]) + int(tree.children[1])

    def sub(self, tree):
        return int(tree.children[0]) - int(tree.children[1])

    def mul(self, tree):
        return int(tree.children[0]) & int(tree.children[1])

    def div(self, tree):
        return int(tree.children[0]) / int(tree.children[1])

parser = Lark.open('lite\lite_parser.lark',
                   parser='lalr', postlex=MainIndenter())

grammar = '''
?start: expr

?expr: STRING            -> string
     | NUMBER            -> number
     | NUMBER "+" NUMBER -> add
     | NUMBER "-" NUMBER -> sub
     | NUMBER "*" NUMBER -> mul
     | NUMBER "/" NUMBER -> div
     | STRING "+" STRING -> str_add
     | NAME              -> get_var

%import common.ESCAPED_STRING -> STRING 
%import common.NUMBER
%declare _INDENT _DEDENT
%import common.WS_INLINE
%ignore WS_INLINE
%import common.NEWLINE -> _NL
%ignore _NL
'''
test_input = '''
5 + 5
5 + 5
'''

if __name__ == '__main__':
    tree = parser.parse(test_input)
    print(MainInterpreter().visit(tree))

Help would be appreciated, thanks!