matcher.add() issue

[Sumanthbab]

Got the below error for code. Pattern seems right list of dict. What am I doing wrong?
Code:

def get_relation(sent):

    doc = nlp(sent)

    # Matcher class object 
    matcher = Matcher(nlp.vocab)

    #define the pattern 
    pattern = [{'DEP':'ROOT'}, {'DEP':'prep','OP':"?"},{'DEP':'agent','OP':"?"},{'POS':'ADJ','OP':"?"}] 

    matcher.add("matching_1", pattern,on_match=None) 

    matches = matcher(doc)
    k = len(matches) - 1

    span = doc[matches[k][1]:matches[k][2]] 

    return(span.text)

ValueError                                Traceback (most recent call last)
<ipython-input-357-7c50b5fe66fb> in <module>
----> 1 get_relation("23324 John completed the task")

<ipython-input-356-5f074925936c> in get_relation(sent)
      9     pattern = [{'DEP':'ROOT'}, {'DEP':'prep','OP':"?"},{'DEP':'agent','OP':"?"},{'POS':'ADJ','OP':"?"}]
     10 
---> 11     matcher.add("matching_1", pattern,on_match=None)
     12 
     13     matches = matcher(doc)

~\Anaconda3\lib\site-packages\spacy\matcher\matcher.pyx in spacy.matcher.matcher.Matcher.add()

ValueError: [E178] Each pattern should be a list of dicts, but got: {'DEP': 'ROOT'}. Maybe you accidentally passed a single pattern to Matcher.add instead of a list of patterns? If you only want to add one pattern, make sure to wrap it in a list. For example: `matcher.add('matching_1', [pattern])`

[polm]

Like the error says, each pattern should be a list of dicts. When you pass patterns to matcher.add, you don't pass one pattern, you pass a list of patterns. In your case you can fix it like this:

matcher.add("matching_1", [pattern], on_match=None) 

[dnchinmayee]

thank u so much. It really helped me.