code: def parse_adjust_by_(self):
      self.advance_lexer_()
      assert self.is_cur_keyword_("ADJUST_BY")
      adjustment = self.expect_number_()
      self.expect_keyword_("AT")
      size = self.expect_number_()
      return adjustment, size
  
imports: import fontTools.voltLib.ast
  from fontTools.voltLib.lexer import Lexer
  from fontTools.voltLib.error import VoltLibError
  from io import open
label_desc: Use image node_id 18 for calling the Parser obj's underlying member method code with example usage: obj.parse_adjust_by_() and returns: adjustment,  size