 
   @doc """
   Returns a binary which corresponds to the text representation
-  of `some_atom` in UTF8 encoding.
+  of `some_atom` in UTF8 encoding. Allowed in guard clauses.
 
   ## Examples
 

  end

  @doc """
  Concatenates two binaries.

  ## Examples


  @doc """
  Implements the unary operator ! as a macro. It receives any
  argument and returns true if it is false or nil. Returns false
  otherwise. Not allowed in guard clauses.

  ## Examples

