PTransforms that read text files and collect contextual information of the elements in
the input.ContextualTextIO.read().ContextualTextIO.readFiles().from(filepattern), but accepting a ValueProvider.PTransform that reads from one or more text files and returns a bounded PCollection containing one element for each line in the input files.ContextualTextIO.read(), but reads each file in a PCollection of FileIO.ReadableFile, returned by FileIO.readMatches().Row, it provides Metadata associated with each Record when reading
from file(s) using ContextualTextIO.FileIO.MatchConfiguration.withEmptyMatchTreatment(org.apache.beam.sdk.io.fs.EmptyMatchTreatment).ContextualTextIO.Read.from(String) matches a very large number of
files.FileIO.MatchConfiguration.