How do I determine if a column name exists in an array or datasubset?

How do I determine if a column name exists in an array or datasubset?

Say for example, the below expression when executed returns that datasubset has two fields /columns names - firstName and secondName. I want to find out if any string "xyz" is present as a field or column in a datasubset /array.

todatasubset({
type!Column(field: "username", alias: "un", visible: true),
type!Column(field: "firstName", alias: "first", visible: false),
type!Column(field: "lastName", alias: "last", visible: true)
},
a!pagingInfo(startIndex: 1, batchSize: 2, sort:{field: "alias", ascending: true})
)
.data

when executed returns the below result

[field=firstName, alias=first, visible=false], [field=lastName, alias=last, visible=true]

OriginalPostID-152071

OriginalPostID-152071