code: def evaluate(self):
          
  
          # Apply Shunting Yard algorithm to convert the infix expression
          # into Reverse Polish Notation. Since we have a very limited
          # set of operators and binding rules, the implementation becomes
          # really simple. The expression is formed of hamcrest matcher instances
          # and operators identifiers (ints).
          ops = []
          rpn = []
          for token in self.expr:
              if isinstance(token, int):
                  while len(ops) and token <= ops[-1]:
                      rpn.append(ops.pop())
                  ops.append(token)
              else:
                  rpn.append(token)
  
          # Append the remaining operators
          while len(ops):
              rpn.append(ops.pop())
  
          # Walk the RPN expression to create AllOf/AnyOf matchers
          stack = []
          for token in rpn:
              if isinstance(token, int):
                  # Handle the NOT case in a special way since it's unary
                  if token == OPERATOR.NOT:
                      stack[-1] = IsNot(stack[-1])
                      continue
  
                  # Our operators always need two operands
                  if len(stack) < 2:
                      raise RuntimeError('Unable to build a valid expression. Not enough operands available.')
  
                  # Check what kind of matcher we need to create
                  if token == OPERATOR.OR:
                      matcher = hc.any_of(*stack[-2:])
                  else:  # AND, BUT
                      matcher = hc.all_of(*stack[-2:])
  
                  stack[-2:] = [matcher]
              else:
                  stack.append(token)
  
          if len(stack) != 1:
              raise RuntimeError('Unable to build a valid expression. The RPN stack should have just one item.')
  
          matcher = stack.pop()
  
          # If a description has been given include it in the matcher
          if self.description:
              matcher = hc.described_as(self.description, matcher)
  
          return matcher
docs: Converts the current expression into a single matcher, applying
              coordination operators to operands according to their binding rules