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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _AnsiCmd(command_list):
 """Takes a list of SGR values and formats them as an ANSI escape sequence. Args: command_list: List of strings, each string represents an SGR value. e.g. 'fg_blue', 'bg_yellow' Returns: The ANSI escape sequence. Raises: ValueError: if a member of command_list does not map to a valid SGR value. """

  if not isinstance(command_list, list):
    raise ValueError('Invalid list: %s' % command_list)
  # Checks that entries are valid SGR names.
  # No checking is done for sequences that are correct but 'nonsensical'.
  for sgr in command_list:
    if sgr.lower() not in SGR:
      raise ValueError('Invalid or unsupported SGR name: %s' % sgr)
  # Convert to numerical strings.
  command_str = [str(SGR[x.lower()]) for x in command_list]
  # Wrap values in Ansi escape sequence (CSI prefix & SGR suffix).
  return '\033[%sm' % (';'.join(command_str))