the toStatement function is used to replace the 'placeholderIdentifier' to '$#' for postgres sql statement style
Example: "INSERT INTO book (title) VALUES (:title)" to "INSERT INTO book (title) VALUES ($1)"
placeholderIdentifier placeholder identifier character represents the pattern that will be
replaced in the execution of the query by the supplied parameters
params parameters can be a list or a map
Returns String query, List<dynamic> Function(dynamic) make_vals
Postgres uses $# for placeholders https://www.postgresql.org/docs/9.1/sql-prepare.html
the toStatement2 function is used to replace the Question mark '?' to '$1' for sql statement
"INSERT INTO book (title) VALUES (?)" to "INSERT INTO book (title) VALUES ($1)"
Returns String query, List<dynamic> Function(dynamic) make_vals
Postgres uses $# for placeholders https://www.postgresql.org/docs/9.1/sql-prepare.html