docs: def convert_to_underscore_separated(self, name):
          """
          Convert from CamelCase to camel_case
          And substitute illegal metric characters
          """
          metric_name = self.FIRST_CAP_RE.sub(br'\1_\2', ensure_bytes(name))
          metric_name = self.ALL_CAP_RE.sub(br'\1_\2', metric_name).lower()
          metric_name = self.METRIC_REPLACEMENT.sub(br'_', metric_name)
          return self.DOT_UNDERSCORE_CLEANUP.sub(br'.', metric_name).strip(b'_')