query = async (findFn) => {
    const results = []

    for await (const doc of iterator()) {
      if (findFn(doc.value)) {
        results.push(doc.value)
      }
    }

    return results
  }
Queries the document store for documents matching mapper filters.
@function
@param {function(Object)} findFn A function for querying for specific
results.

The findFn function's signature takes the form `function(doc)` where doc
is a document's value property. The function should return true if the
document should be included in the results, false otherwise.
@return {Array} Found documents.
@memberof module:Databases.Databases-Documents
@instance