Swig error: member function already defined or declared

Question

I'm pretty much a swig novice so I hope that the problem I'm running into is a basic one. My problem is that I can't seem to get swig to compile an unordered_map. Here's a MWE. Note that I eventually want to use the unordered map as a python dictionary.

// UsingUnorderedMap.h
#include <string>
#include <unordered_map>

class UsingUnorderedMap{
public:
    UsingUnorderedMap() = default;
    const std::unordered_map<std::string, double> &getStringDoubleMap() const;
    void setStringDoubleMap(const std::unordered_map<std::string, double> &stringDoubleMap);
private:
    std::unordered_map<std::string, double> StringDoubleMap;
};

// UsingUnorderedMap.cpp
#include "UsingUnorderedMap.h"

const std::unordered_map<std::string, double> &UsingUnorderedMap::getStringDoubleMap() const {
    return StringDoubleMap;
}

void UsingUnorderedMap::setStringDoubleMap(const std::unordered_map<std::string, double> &stringDoubleMap) {
    StringDoubleMap = stringDoubleMap;
}

// UsingUnorderedMap.i
%module UsingUnorderedMap

%{
#include "UsingUnorderedMap.h"
%}

%include "std_string.i"
%include "std_pair.i"
%include "std_unordered_map.i"

namespace std {
    %template(StringDoubleDict) unordered_map<string, double>;
}

%include "UsingUnorderedMap.h"

And you can build it with CMake using :

# CMakeLists.txt
include(UseSWIG)

set_property(SOURCE UsingUnorderedMap.i PROPERTY CPLUSPLUS ON)

swig_add_library(UsingUnorderedMap
        LANGUAGE python
        TYPE MODULE
        SOURCES UsingUnorderedMap.i UsingUnorderedMap.h UsingUnorderedMap.cpp)

set_target_properties(UsingUnorderedMap
        PROPERTIES LANGUAGE CXX)

target_include_directories(UsingUnorderedMap PUBLIC
        ${Python_INCLUDE_DIRS}
        ${CMAKE_CURRENT_SOURCE_DIR}
        )
target_link_libraries(UsingUnorderedMap PUBLIC ${Python_LIBRARIES})

install(TARGETS UsingUnorderedMap DESTINATION UsingUnorderedMap)
install(FILES ${CMAKE_CURRENT_BINARY_DIR}/UsingUnorderedMap.py DESTINATION UsingUnorderedMap)

The error I get is:

C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.28.29333\include\unordered_map(133): error C2535: 'std::unordered_map<std::string,double,std::less<std::string>,std::allocator<std::pair<const std::string,double>>,std::allocator<std::pair<const std::string,double>>>::unordered_map(unsigned __int64,const std::less<std::string> &,const std::allocator<std::pair<const std::string,double>> &)': member function already defined or declared
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.28.29333\include\unordered_map(128): note: see declaration of 'std::unordered_map<std::string,double,std::less<std::string>,std::allocator<std::pair<const std::string,double>>,std::allocator<std::pair<const std::string,double>>>::unordered_map'
D:\LearnSwig\cmake-build-release-visual-studio\src\UsingUnorderedMap\CMakeFiles\UsingUnorderedMap.dir\UsingUnorderedMapPYTHON_wrap.cxx(5059): note: see reference to class template instantiation 'std::unordered_map<std::string,double,std::less<std::string>,std::allocator<std::pair<const std::string,double>>,std::allocator<std::pair<const std::string,double>>>' being compiled
...

Any help or advice you have would be greatly appreciated, thanks.