class SQLite3::Database

def trace(data = nil, &block)

any existing tracer will be uninstalled.
argument, and the SQL statement executed. If the block is +nil+,
statement executed. The block receives a two parameters: the +data+
Installs (or removes) a block that will be invoked for every SQL 
def trace(data = nil, &block)
  @driver.trace(@handle, data, &block)
end