How to use the expression.parseExpression function in Expression

paths[FUNCTION] = self.subroutine_decl
    paths[RETURN] = self.return_statement
    # paths[VAR] = self.var_statement
    # paths[STATE] = self.state_block
    # paths[FOR] = self.for_block
    paths[RBRACKET] = self.right_bracket
    paths[NEWLINE] = self.new_line

    next_token = self.tokens.next()

    if next_token.match in paths:
      paths[next_token.match]()
      return

    # otherwise, parse as expression
    expr = expression.parseExpression(self.tokens)
    if expr:
      expr.eval(self.builder)
      return

    # if we got this far then we don't know what the hell to do
    pdb.set_trace()
    raise parse_errors.NotAStatement(next_token)

def if_statement(self):
    self.tokens.consume(IF)
    self.tokens.startSkipping(NEWLINE)

    self.tokens.consume(LPAREN)

    # parse the condition expression
    first_condition_token = self.tokens.next()
    condition_expr = expression.parseExpression(self.tokens)
    condition_term = condition_expr.eval(self.builder)

    if condition_term == None:
      raise parse_errors.ExpectedExpression(first_condition_token)
    
    self.tokens.consume(RPAREN)

    cond_block = self.builder.startConditionalBlock(condition=condition_term)

    self.block_body()