Unable to apply Regexp in Filter

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I want to search user as regexp But Unable to Filter With Regexp

Please list the high level idea of what you want to do

What I did

Request
query {
        feed(func: near(geolocation, [28.755177456, 77.19569813],1000), 
  
        first: 5, 
        offset: 0, 
        orderdesc: posted_at)
        @filter(eq(is_hidden, 0) AND 
          eq(category, "moment") AND
          eq(is_curated, false) AND
           eq(post_type, "trip") And
           regexp(post_user," /.*sandeep.*/i") and
           
             
            
          
          NOT has(vendor_id)){
          uid
          expand(Moment){
            uid
            expand(Media)
          }
          _location: ~moments {
            uid
            expand(Location)
            _trip: ~locations {
              uid
              expand(Trip)
            }
          }
        }
      }

Please list the things you have tried.

"errors": [
    {
      "message": ": Function 'regexp' requires 2 arguments, but got 1 ([ /.*alien.*/i])",
      "extensions": {
        "code": "ErrorInvalidRequest"
      }
    }
  ]

I have queried on the Basis of Geolocation data now I want to filter on the Basis Or regexp but when I apply it in Filter part Its Give Error

"errors": [
    {
      "message": ": Function 'regexp' requires 2 arguments, but got 1 ([ /.*alien.*/i])",
      "extensions": {
        "code": "ErrorInvalidRequest"
      }
    }
  ]

Remove the quotes.

It should be

regexp([email protected], /.*sandeep.*/i)