This method is used inside of several different objects to determine if special behavior is needed in the constructor.
Special behavior is needed if the array passed in as args has true or false as its value, and if the second element of args is a hash.
Retrieves the pre-configured API key key or terminates interaction with an error.
Turns email_address into an OpenSSL::X509::Name
@return [Array<Vertex>] the vertices of {#graph} that have an edge with
`self` as their {Edge#destination}
Removes a possibility from ‘self` @return [PossibilityState] a state with a single possibility,
the possibility that was removed from `self`