code: def _parse_header_id(line):
      
      if type(line) is not binary_type:
          raise TypeError("Expected header line to be of type %s but got %s" % (
              binary_type, type(line)))
  
      if len(line) <= 1:
          raise ValueError("No identifier on FASTA line")
  
      # split line at first space to get the unique identifier for
      # this sequence
      space_index = line.find(b" ")
      if space_index >= 0:
          identifier = line[1:space_index]
      else:
          identifier = line[1:]
  
      # annoyingly Ensembl83 reformatted the transcript IDs of its
      # cDNA FASTA to include sequence version numbers
      # .e.g.
      # "ENST00000448914.1" instead of "ENST00000448914"
      # So now we have to parse out the identifier
      dot_index = identifier.find(b".")
      if dot_index >= 0:
          identifier = identifier[:dot_index]
  
      return identifier.decode("ascii")
docs: Pull the transcript or protein identifier from the header line
      which starts with '>'