nl_tokens: The base implementation of _ . flatten without support for callback shorthands or thisArg binding .
pl_tokens: function baseFlatten ( array , isShallow , isArgArrays , fromIndex ) { var index = ( fromIndex || 0 ) - 1 , length = array ? array . length : 0 , result = [ ] ; while ( ++ index < <mask> ) { var value = array [ index ] ; if ( value && typeof value == 'object' && typeof value . length == 'number' && ( isArray ( value ) || isArguments ( value ) ) ) { // recursively flatten arrays (susceptible to call stack limits) if ( ! isShallow ) { value = baseFlatten ( value , isShallow , isArgArrays ) ; } var valIndex = - 1 , valLength = value . length , resIndex = result . length ; result . length += valLength ; while ( ++ valIndex < valLength ) { result [ resIndex ++ ] = value [ valIndex ] ; } } else if ( ! isArgArrays ) { result . push ( value ) ; } } return result ; }