Undeclared field: 'keys' (iterator call)

[readysloth]

Hi all again!

I want to use filter function on keys of some table, so i wrote this code: 
    
    
    my_very_own_table.keys.to_seq.filter( ... )
    
    
    Run

but instead of executable i get this error: 
    
    
    Error: undeclared field: 'keys'
    
    found *list of iterators with same name*
    
    
    Run

Why i get this? Because in for loop it works as usual...