code: def parse(self, scope):
          
          assert (len(self.tokens) == 3)
          expr = self.process(self.tokens, scope)
          A, O, B = [
              e[0] if isinstance(e, tuple) else e for e in expr
              if str(e).strip()
          ]
          try:
              a, ua = utility.analyze_number(A, 'Illegal element in expression')
              b, ub = utility.analyze_number(B, 'Illegal element in expression')
          except SyntaxError:
              return ' '.join([str(A), str(O), str(B)])
          if (a is False or b is False):
              return ' '.join([str(A), str(O), str(B)])
          if ua == 'color' or ub == 'color':
              return color.Color().process((A, O, B))
          if a == 0 and O == '/':
              # NOTE(saschpe): The ugliest but valid CSS since sliced bread: 'font: 0/1 a;'
              return ''.join([str(A), str(O), str(B), ' '])
          out = self.operate(a, b, O)
          if isinstance(out, bool):
              return out
          return self.with_units(out, ua, ub)
docs: Parse Node
          args:
              scope (Scope): Scope object
          raises:
              SyntaxError
          returns:
              str