[Typescript] Invalid enum variable name for <> (NotEqual)

Description

For an enum with symbol-name "<>" the typescript-fetch generator generates an empty var name (but I guess it doesn't only affect typescript-fetch).

Result (the second last line is invalid):

export enum FilterTypeEnum {
        Equal = <any> '=',
        GreaterThanOrEqualTo = <any> '>=',
        GreaterThan = <any> '>',
        LessThanOrEqualTo = <any> '<=',
        LessThan = <any> '<',
          = <any> '<>'
    }

Swagger-codegen version

2.4.0-SNAPSHOT

Swagger declaration file content or url

[...]
"AttributeFilter" : {
      "type" : "object",
      "properties" : {
        "filterType" : {
          "type" : "string",
          "description" : "Default is equals.",
          "enum" : [ "=", ">=", ">", "<=", "<", "<>" ]
        },
      },
    },
[...]

Command line used for generation

n/a

Steps to reproduce

see above

Related issues/PRs

None found

Suggest a fix/enhancement

Extend DefaultCodegen.java with an additional specialCharReplacements.put("<>", "Unequal");

Start in DefaultCodegen.java, where special character replacements are defined, and inspect how the typescript-fetch generator maps enum symbols to variable names. Reproduce the declaration using the provided enum values, then verify that the <> value receives a valid name and the generated TypeScript enum contains no empty identifier.