code: def adb_path(cls):
          
          if cls.__adb_cmd is None:
              if "ANDROID_HOME" in os.environ:
                  filename = "adb.exe" if os.name == 'nt' else "adb"
                  adb_dir = os.path.join(os.environ["ANDROID_HOME"], "platform-tools")
                  adb_cmd = os.path.join(adb_dir, filename)
                  if not os.path.exists(adb_cmd):
                      raise EnvironmentError(
                          "Adb not found in $ANDROID_HOME/platform-tools path: %s." % adb_dir)
              else:
                  import distutils
                  if "spawn" not in dir(distutils):
                      import distutils.spawn
                  adb_cmd = distutils.spawn.find_executable("adb")
                  if adb_cmd:
                      adb_cmd = os.path.realpath(adb_cmd)
                  else:
                      raise EnvironmentError("$ANDROID_HOME environment not set.")
              cls.__adb_cmd = adb_cmd
          return cls.__adb_cmd
docs: return adb binary full path