diff --git a/pandas/_libs/tslibs/fields.pyx b/pandas/_libs/tslibs/fields.pyx
index 684344ceb9002..1af9cd619c5f9 100644
--- a/pandas/_libs/tslibs/fields.pyx
+++ b/pandas/_libs/tslibs/fields.pyx
@@ -40,7 +40,7 @@ def get_time_micros(ndarray[int64_t] dtindex):
     return micros
 
 
-def build_field_sarray(ndarray[int64_t] dtindex):
+def build_field_sarray(int64_t[:] dtindex):
     """
     Datetime as int64 representation to a structured array of fields
     """
@@ -542,7 +542,7 @@ def get_date_field(ndarray[int64_t] dtindex, object field):
 
 @cython.wraparound(False)
 @cython.boundscheck(False)
-def get_timedelta_field(ndarray[int64_t] tdindex, object field):
+def get_timedelta_field(int64_t[:] tdindex, object field):
     """
     Given a int64-based timedelta index, extract the days, hrs, sec.,
     field and return an array of these values.
diff --git a/pandas/_libs/tslibs/timedeltas.pxd b/pandas/_libs/tslibs/timedeltas.pxd
index eda4418902513..c02a840281266 100644
--- a/pandas/_libs/tslibs/timedeltas.pxd
+++ b/pandas/_libs/tslibs/timedeltas.pxd
@@ -3,8 +3,6 @@
 from numpy cimport int64_t
 
 # Exposed for tslib, not intended for outside use.
-cdef parse_timedelta_string(object ts)
-cpdef int64_t cast_from_unit(object ts, object unit) except? -1
+cdef int64_t cast_from_unit(object ts, object unit) except? -1
 cpdef int64_t delta_to_nanoseconds(delta) except? -1
 cpdef convert_to_timedelta64(object ts, object unit)
-cpdef array_to_timedelta64(object[:] values, unit=*, errors=*)
diff --git a/pandas/_libs/tslibs/timedeltas.pyx b/pandas/_libs/tslibs/timedeltas.pyx
index 9c8be1901d1dc..d4e0e7f8ad72d 100644
--- a/pandas/_libs/tslibs/timedeltas.pyx
+++ b/pandas/_libs/tslibs/timedeltas.pyx
@@ -119,8 +119,6 @@ def ints_to_pytimedelta(int64_t[:] arr, box=False):
 # ----------------------------------------------------------------------
 
 cpdef int64_t delta_to_nanoseconds(delta) except? -1:
-    if util.is_array(delta):
-        return delta.astype('m8[ns]').astype('int64')
     if hasattr(delta, 'nanos'):
         return delta.nanos
     if hasattr(delta, 'delta'):
@@ -129,10 +127,12 @@ cpdef int64_t delta_to_nanoseconds(delta) except? -1:
         return delta.astype("timedelta64[ns]").item()
     if is_integer_object(delta):
         return delta
+    if PyDelta_Check(delta):
+        return (delta.days * 24 * 60 * 60 * 1000000 +
+                delta.seconds * 1000000 +
+                delta.microseconds) * 1000
 
-    return (delta.days * 24 * 60 * 60 * 1000000 +
-            delta.seconds * 1000000 +
-            delta.microseconds) * 1000
+    raise TypeError(type(delta))
 
 
 cpdef convert_to_timedelta64(object ts, object unit):
@@ -198,7 +198,7 @@ cpdef convert_to_timedelta64(object ts, object unit):
     return ts.astype('timedelta64[ns]')
 
 
-cpdef array_to_timedelta64(object[:] values, unit='ns', errors='raise'):
+def array_to_timedelta64(object[:] values, unit='ns', errors='raise'):
     """
     Convert an ndarray to an array of timedeltas. If errors == 'coerce',
     coerce non-convertible objects to NaT. Otherwise, raise.
@@ -235,7 +235,7 @@ cpdef array_to_timedelta64(object[:] values, unit='ns', errors='raise'):
     return iresult.base  # .base to access underlying np.ndarray
 
 
-cpdef inline int64_t cast_from_unit(object ts, object unit) except? -1:
+cdef inline int64_t cast_from_unit(object ts, object unit) except? -1:
     """ return a casting of the unit represented to nanoseconds
         round the fractional part of a float to our precision, p """
     cdef:
diff --git a/pandas/_libs/tslibs/timezones.pyx b/pandas/_libs/tslibs/timezones.pyx
index b7e4de81da35c..1fc1347c8b9e3 100644
--- a/pandas/_libs/tslibs/timezones.pyx
+++ b/pandas/_libs/tslibs/timezones.pyx
@@ -322,7 +322,7 @@ cpdef bint tz_compare(object start, object end):
     return get_timezone(start) == get_timezone(end)
 
 
-cpdef tz_standardize(object tz):
+def tz_standardize(tz: object):
     """
     If the passed tz is a pytz timezone object, "normalize" it to the a
     consistent version
diff --git a/pandas/tests/tslibs/test_timedeltas.py b/pandas/tests/tslibs/test_timedeltas.py
new file mode 100644
index 0000000000000..939c2b828a75f
--- /dev/null
+++ b/pandas/tests/tslibs/test_timedeltas.py
@@ -0,0 +1,40 @@
+# -*- coding: utf-8 -*-
+import numpy as np
+import pytest
+
+import pandas as pd
+from pandas._libs.tslibs.timedeltas import delta_to_nanoseconds
+
+
+def test_delta_to_nanoseconds():
+    obj = np.timedelta64(14, 'D')
+    result = delta_to_nanoseconds(obj)
+    assert result == 14 * 24 * 3600 * 1e9
+
+    obj = pd.Timedelta(minutes=-7)
+    result = delta_to_nanoseconds(obj)
+    assert result == -7 * 60 * 1e9
+
+    obj = pd.Timedelta(minutes=-7).to_pytimedelta()
+    result = delta_to_nanoseconds(obj)
+    assert result == -7 * 60 * 1e9
+
+    obj = pd.offsets.Nano(125)
+    result = delta_to_nanoseconds(obj)
+    assert result == 125
+
+    obj = 1
+    result = delta_to_nanoseconds(obj)
+    assert obj == 1
+
+    obj = np.int64(2)
+    result = delta_to_nanoseconds(obj)
+    assert obj == 2
+
+    obj = np.int32(3)
+    result = delta_to_nanoseconds(obj)
+    assert result == 3
+
+    obj = np.array([123456789], dtype='m8[ns]')
+    with pytest.raises(TypeError):
+        delta_to_nanoseconds(obj)