Extract python version from explicit main group (poetry)

As documented here
https://python-poetry.org/docs/managing-dependencies/#dependency-groups

```toml
[tool.poetry.dependencies]
```
and
```toml
[tool.poetry.group.main.dependencies]
```
Are equivalent

__tests__/utils.test.ts

@@ -126,6 +126,18 @@ describe('Version from file test', () => {
       expect(_fn(pythonVersionFilePath)).toEqual([pythonVersion]);
     }
   );
+  it.each([getVersionInputFromTomlFile, getVersionInputFromFile])(
+    'Version from poetry with explicit main group pyproject.toml test',
+    async _fn => {
+      await io.mkdirP(tempDir);
+      const pythonVersionFileName = 'pyproject.toml';
+      const pythonVersionFilePath = path.join(tempDir, pythonVersionFileName);
+      const pythonVersion = '>=3.7.0';
+      const pythonVersionFileContent = `[tool.poetry.group.main.dependencies]\npython = "${pythonVersion}"`;
+      fs.writeFileSync(pythonVersionFilePath, pythonVersionFileContent);
+      expect(_fn(pythonVersionFilePath)).toEqual([pythonVersion]);
+    }
+  );
   it.each([getVersionInputFromTomlFile, getVersionInputFromFile])(
     'Version undefined',
     async _fn => {

src/utils.ts

@@ -228,15 +228,23 @@ export function getVersionInputFromTomlFile(versionFile: string): string[] {
 
   if ('project' in pyprojectConfig) {
     // standard project metadata (PEP 621)
-    keys = ['project', 'requires-python'];
+    keys = [['project', 'requires-python']];
   } else {
     // python poetry
-    keys = ['tool', 'poetry', 'dependencies', 'python'];
+    keys = [
+      // implicit group main
+      ['tool', 'poetry', 'dependencies', 'python'],
+      // explicit group main
+      ['tool', 'poetry', 'group', 'main', 'dependencies', 'python']
+    ];
   }
   const versions = [];
-  const version = extractValue(pyprojectConfig, keys);
-  if (version !== undefined) {
-    versions.push(version);
+  for (const key of keys) {
+    const version = extractValue(pyprojectConfig, key);
+    if (version !== undefined) {
+      versions.push(version);
+      break;
+    }
   }
 
   core.info(`Extracted ${versions} from ${versionFile}`);