public Builder declarationFile(String declarationFile) {
            this.declarationFile = declarationFile;
            return this;
        }
Sets the filename of where this symbol is declared.

<p>This value defaults to the value provided for {@link #definitionFile}
if not present. One of a {@code definitionFile} or a {@code declarationFile}
must be provided for every Symbol.

@param declarationFile Filename of where the symbol is declared.
@return Returns the builder.
smithy-codegen-core/src/main/java/software/amazon/smithy/codegen/core/Symbol.java