code: def prepare_input_source(source, base=""):
      """This function takes an InputSource and an optional base URL and
      returns a fully resolved InputSource object ready for reading."""
  
      if isinstance(source, os.PathLike):
          source = os.fspath(source)
      if isinstance(source, str):
          source = xmlreader.InputSource(source)
      elif hasattr(source, "read"):
          f = source
          source = xmlreader.InputSource()
          if isinstance(f.read(0), str):
              source.setCharacterStream(f)
          else:
              source.setByteStream(f)
          if hasattr(f, "name") and isinstance(f.name, str):
              source.setSystemId(f.name)
  
      if (
          source.getCharacterStream() is None
          and source.getByteStream() is None
      ):
          sysid = source.getSystemId()
          basehead = os.path.dirname(os.path.normpath(base))
          sysidfilename = os.path.join(basehead, sysid)
          if os.path.isfile(sysidfilename):
              source.setSystemId(sysidfilename)
              f = open(sysidfilename, "rb")
          else:
              source.setSystemId(urllib.parse.urljoin(base, sysid))
              f = urllib.request.urlopen(source.getSystemId())
  
          source.setByteStream(f)
  
      return source
  
imports: import os, urllib.parse, urllib.request
  import io
  import codecs
  from .None import handler
  from .None import xmlreader
label_desc: Use image node_id 6 for calling a global function with example usage: prepare_input_source(source, base) and returns: source