diff --git a/dedoc/metadata_extractors/abstract_metadata_extractor.py b/dedoc/metadata_extractors/abstract_metadata_extractor.py
index 90f8b5f4..b79bda60 100644
--- a/dedoc/metadata_extractors/abstract_metadata_extractor.py
+++ b/dedoc/metadata_extractors/abstract_metadata_extractor.py
@@ -29,7 +29,7 @@ def extract_metadata(self,
                      converted_filename: str,
                      original_filename: str,
                      parameters: Optional[dict] = None,
-                     other_fields: Optional[dict] = None) -> Dict[str]:
+                     other_fields: Optional[dict] = None) -> dict:
         """
         Extract metadata from file if possible, i.e. method :meth:`can_extract` returned True.
 
diff --git a/dedoc/metadata_extractors/concrete_metadata_extractors/base_metadata_extractor.py b/dedoc/metadata_extractors/concrete_metadata_extractors/base_metadata_extractor.py
index 6f4c180c..dae404b5 100644
--- a/dedoc/metadata_extractors/concrete_metadata_extractors/base_metadata_extractor.py
+++ b/dedoc/metadata_extractors/concrete_metadata_extractors/base_metadata_extractor.py
@@ -40,7 +40,7 @@ def extract_metadata(self,
                          converted_filename: str,
                          original_filename: str,
                          parameters: Optional[dict] = None,
-                         other_fields: Optional[dict] = None) -> Dict[str]:
+                         other_fields: Optional[dict] = None) -> dict:
         """
         Gets the basic meta-information about the file.
         Look to the :meth:`~dedoc.metadata_extractors.AbstractMetadataExtractor.extract_metadata` documentation to get the information about parameters.
diff --git a/dedoc/metadata_extractors/concrete_metadata_extractors/docx_metadata_extractor.py b/dedoc/metadata_extractors/concrete_metadata_extractors/docx_metadata_extractor.py
index 57401b3c..07f3e02c 100644
--- a/dedoc/metadata_extractors/concrete_metadata_extractors/docx_metadata_extractor.py
+++ b/dedoc/metadata_extractors/concrete_metadata_extractors/docx_metadata_extractor.py
@@ -42,7 +42,7 @@ def extract_metadata(self,
                          converted_filename: str,
                          original_filename: str,
                          parameters: dict = None,
-                         other_fields: Optional[dict] = None) -> Dict[str]:
+                         other_fields: Optional[dict] = None) -> dict:
         """
         Add the predefined list of metadata for the docx documents.
         Look to the :meth:`~dedoc.metadata_extractors.AbstractMetadataExtractor.extract_metadata` documentation to get the information about parameters.
diff --git a/dedoc/metadata_extractors/concrete_metadata_extractors/image_metadata_extractor.py b/dedoc/metadata_extractors/concrete_metadata_extractors/image_metadata_extractor.py
index 4ab08aed..72478fe9 100644
--- a/dedoc/metadata_extractors/concrete_metadata_extractors/image_metadata_extractor.py
+++ b/dedoc/metadata_extractors/concrete_metadata_extractors/image_metadata_extractor.py
@@ -72,7 +72,7 @@ def extract_metadata(self,
                      converted_filename: str,
                      original_filename: str,
                      parameters: dict = None,
-                     other_fields: Optional[dict] = None) -> UnstructuredDocument:
+                     other_fields: Optional[dict] = None) -> dict:
         """
         Add the predefined list of metadata for images.
         Look to the :meth:`~dedoc.metadata_extractors.AbstractMetadataExtractor.extract_metadata` documentation to get the information about parameters.
diff --git a/dedoc/metadata_extractors/concrete_metadata_extractors/note_metadata_extarctor.py b/dedoc/metadata_extractors/concrete_metadata_extractors/note_metadata_extarctor.py
index 7001d6c5..4cf5c60b 100644
--- a/dedoc/metadata_extractors/concrete_metadata_extractors/note_metadata_extarctor.py
+++ b/dedoc/metadata_extractors/concrete_metadata_extractors/note_metadata_extarctor.py
@@ -36,7 +36,7 @@ def extract_metadata(self,
                          converted_filename: str,
                          original_filename: str,
                          parameters: dict = None,
-                         other_fields: Optional[dict] = None) -> Dict[str]:
+                         other_fields: Optional[dict] = None) -> dict:
         """
         Add the predefined list of metadata for the .note.pickle documents.
         Look to the :meth:`~dedoc.metadata_extractors.AbstractMetadataExtractor.extract_metadata` documentation to get the information about parameters.
diff --git a/dedoc/metadata_extractors/concrete_metadata_extractors/pdf_metadata_extractor.py b/dedoc/metadata_extractors/concrete_metadata_extractors/pdf_metadata_extractor.py
index 26934d8f..927284a0 100644
--- a/dedoc/metadata_extractors/concrete_metadata_extractors/pdf_metadata_extractor.py
+++ b/dedoc/metadata_extractors/concrete_metadata_extractors/pdf_metadata_extractor.py
@@ -65,7 +65,7 @@ def extract_metadata(self,
                          converted_filename: str,
                          original_filename: str,
                          parameters: dict = None,
-                         other_fields: Optional[dict] = None) -> Dict[str]:
+                         other_fields: Optional[dict] = None) -> dict:
         """
         Add the predefined list of metadata for the pdf documents.
         Look to the :meth:`~dedoc.metadata_extractors.AbstractMetadataExtractor.extract_metadata` documentation to get the information about parameters.
diff --git a/dedoc/metadata_extractors/metadata_extractor_composition.py b/dedoc/metadata_extractors/metadata_extractor_composition.py
index 296c3f60..0f68f1cf 100644
--- a/dedoc/metadata_extractors/metadata_extractor_composition.py
+++ b/dedoc/metadata_extractors/metadata_extractor_composition.py
@@ -22,7 +22,7 @@ def extract_metadata(self,
                          converted_filename: str,
                          original_filename: str,
                          parameters: Optional[dict] = None,
-                         other_fields: Optional[dict] = None) -> Dict[str]:
+                         other_fields: Optional[dict] = None) -> dict:
         """
         Add metadata to the document using one of the extractors if suitable extractor was found.
         Look to the method :meth:`~dedoc.metadata_extractors.AbstractMetadataExtractor.extract_metadata` of the class