class Hash

def stringify_keys!

Experimental RBS support (using type sampling data from the type_fusion project). 

def stringify_keys!: () -> untyped

This signature was generated using 1 sample from 1 application.

+stringify_keys+, but modifies +self+.
Destructively converts all keys to strings. Same as 
def stringify_keys!
  transform_keys!(&:to_s)
end