public String getDeclarationFile() {
        return declarationFile;
    }
Gets the location/filename in which the symbol is declared.

<p>Code generators should write the generated code for this
symbol's declaration in a file with the same name that is
returned from this method. Not all languages separate a symbol's
definition from its declaration. This method is useful for things
like C and C++ header files.

<p>This method returns an empty string if no value was provided
in the builder.

@return The name of the file the symbol is declared.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/Symbol.java