Segments are fields with enumerated values, so filtering on them is done with enumeration options. To know which are options are available in a field, call the Metadata API. The order of the options never changes, but new options may be added.

Use the in filter, and the values in the array should be the IDs of the options.

Metadata query

query { fields(ids:["e_bp_wm_client_aum_alt"]){
    nodes{
      options{
        id
        name
      }
    }
  }
}

Data query

query getData($filter: Filter){
  feedback(
    filter: $filter
  ){
    nodes{ #object with data
        fieldData(fieldId:"e_responsedate"){ values}
    }
  }
}

Variable

{
  "filter": { "fieldIds": ["e_bp_wm_client_aum_alt"], "in": "2"}
}