How to get information about the sequence behind the new Identity Column in Postgres 10? (GENERATED { ALWAYS | BY DEFAULT } AS IDENTITY)
It appears you use the same functions as before:

https://www.postgresql.org/docs/10/static/functions-info.html


  pg_get_serial_sequence returns the name of the sequence associated
  with a column, or NULL if no sequence is associated with the column.
  If the column is an identity column, the associated sequence is the
  sequence internally created for the identity column. For columns
  created using one of the serial types (serial, smallserial,
  bigserial), it is the sequence created for that serial column
  definition. In the latter case, this association can be modified or
  removed with ALTER SEQUENCE OWNED BY. (The function probably should
  have been called pg_get_owned_sequence; its current name reflects the
  fact that it has typically been used with serial or bigserial
  columns.) The first input parameter is a table name with optional
  schema, and the second parameter is a column name. Because the first
  parameter is potentially a schema and table, it is not treated as a
  double-quoted identifier, meaning it is lower cased by default, while
  the second parameter, being just a column name, is treated as
  double-quoted and has its case preserved. The function returns a value
  suitably formatted for passing to sequence functions (see Section
  9.16). A typical use is in reading the current value of a sequence for an identity or serial column, for example:
  
  SELECT currval(pg_get_serial_sequence('sometable', 'id'));