code: def find(name):
      
  
      if op.exists(name):
          return name
  
      path = op.dirname(__file__) or '.'
  
      paths = [path] + config['include_path']
  
      for path in paths:
          filename = op.abspath(op.join(path, name))
          if op.exists(filename):
              return filename
  
          for d in os.listdir(path):
              fullpath = op.abspath(op.join(path, d))
              if op.isdir(fullpath):
                  filename = op.abspath(op.join(fullpath, name))
                  if op.exists(filename):
                      return filename
  
      return None
docs: Locate a filename into the shader library.