Class Membership (1.8.2) 

Membership(value)

Whether the binding includes the member.

Values: MEMBERSHIP_UNSPECIFIED (0): Reserved for future use. MEMBERSHIP_INCLUDED (1): The binding includes the member. The member can be included directly or indirectly. For example:

    -  A member is included directly if that member is listed in
       the binding.
    -  A member is included indirectly if that member is in a
       Google group or G Suite domain that is listed in the
       binding.
MEMBERSHIP_NOT_INCLUDED (2):
    The binding does not include the member.
MEMBERSHIP_UNKNOWN_INFO_DENIED (3):
    The sender of the request is not allowed to
    access the binding.
MEMBERSHIP_UNKNOWN_UNSUPPORTED (4):
    The member is an unsupported type. Only
    Google Accounts and service accounts are
    supported.