def regex(field_uid, pattern, options="")
      hash = {
        "#{field_uid}" => {
          "$regex": pattern
        }
      }

      hash["#{field_uid}"]["$options"] = options if !options.empty? || !options.nil?

      add_query_hash(hash)
    end
def regex(field_uid, pattern, options="")
      hash = {
        "#{field_uid}" => {
          "$regex": pattern
        }
      }

      hash["#{field_uid}"]["$options"] = options if !options.empty? || !options.nil?

      add_query_hash(hash)
    end
Add a regular expression constraint for finding string values that match the provided regular expression. This may be slow for large data sets.
 @param [String] field_uid  The key to be constrained.
 @param [String] pattern  The regular expression pattern to match.
 @param [String] options  Regex options

 Example:
    @query = @stack.content_type('product').query
    @query.regex('title', '.*Mobile.*', 'i') # Search without case sensitivity

 @return [Contentstack::Query]